The Thermarest MondoKing 3D is the biggest Therm-a-Rest mattress ever. Vertical sidewalls create 20% more usable sleep surface so you have room to sleep like starfish. Dual valves allow compressible foam core to expand and inflate quickly when unpacked. A new and improved stuff sack with easy-carry handle is also included. 4 in (10 cm) of stabilized loft provides the comfort of home anywhere. Vertical sidewalls maximize useable sleep surface. Foam core delivers all-season warmth to assure a great night's rest anytime. Dual valves allow compressible foam core to expand/inflate when unpacked; just a few breaths top it off to your ideal firmness. Mates perfectly with another 3D mattress.
The Thermarest MondoKing 3D is the biggest Therm-a-Rest mattress ever. Vertical sidewalls create 20% more usable sleep surface so you have room to sleep like starfish. Dual valves allow compressible foam core to expand and inflate quickly when unpacked. A new and improved stuff sack with easy-carry handle is also included. 4 in (10 cm) of stabilized loft provides the comfort of home anywhere. Vertical sidewalls maximize useable sleep surface. Foam core delivers all-season warmth to assure a great night's rest anytime. Dual valves allow compressible foam core to expand/inflate when unpacked; just a few breaths top it off to your ideal firmness. Mates perfectly with another 3D mattress.
in 2 offers
The lowest price for Thermarest MondoKing 3D Blue Depths Mattress - XX-Large right now is $569.90 at Great Escape Camping, compared across 2 retailers.
The all-time low was $261.20 on 4 July 2025 — today's price is 118% above the lowest ever. It has been notably cheaper before — worth setting a price alert.
Prices last updated 12 May 2026.
Thermarest MondoKing 3D Blue Depths Mattress - XX-Large
The Thermarest MondoKing 3D is the biggest Therm-a-Rest mattress ever. Vertical sidewalls create 20% more usable sleep surface so you have room to sleep like starfish. Dual valves allow compressible foam core to expand and inflate quickly when unpacked. A new and improved stuff sack with easy-carry handle is also included. 4 in (10 cm) of stabilized loft provides the comfort of home anywhere. Vertical sidewalls maximize useable sleep surface. Foam core delivers all-season warmth to assure a great night's rest anytime. Dual valves allow compressible foam core to expand/inflate when unpacked; just a few breaths top it off to your ideal firmness. Mates perfectly with another 3D mattress.
The Thermarest MondoKing 3D is the biggest Therm-a-Rest mattress ever. Vertical sidewalls create 20% more usable sleep surface so you have room to sleep like starfish. Dual valves allow compressible foam core to expand and inflate quickly when unpacked. A new and improved stuff sack with easy-carry handle is also included. 4 in (10 cm) of stabilized loft provides the comfort of home anywhere. Vertical sidewalls maximize useable sleep surface. Foam core delivers all-season warmth to assure a great night's rest anytime. Dual valves allow compressible foam core to expand/inflate when unpacked; just a few breaths top it off to your ideal firmness. Mates perfectly with another 3D mattress.
Last updated at 12/05/2026 01:46:03
Thermarest Mondoking 3D XXL Sleep Mat
Free delivery between 15–22 May
Thermarest Mondoking 3d Xx Large Sleep Mat
Free delivery
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originally posted on REI
I've used lots of sleeping pads over the decades. As my wife and I are now 60, comfort while sleeping is more difficult to come by when camping. I bought two of these Mondo XLs and they are wonderful. Sleep as well as if I'm in my own bed.Put two of them together with sheets (fitted and regular) for a queen size bed - works perfectly. We have used them on 5 trips of 1+ weeks each this summer. No problems at all. Take a couple of minutes to pack up in the morning. Fold it in thirds, crush out the air. Close the valves. Then roll it up like a normal foam mattress pad. When you get close to the end, open the valves and let the air out. Then repeat this process once more and they will slide right into their carrying bags.One note: DO NOT KEEP THEM IN THE STORAGE ... MoreI've used lots of sleeping pads over the decades. As my wife and I are now 60, comfort while sleeping is more difficult to come by when camping. I bought two of these Mondo XLs and they are wonderful. Sleep as well as if I'm in my own bed.Put two of them together with sheets (fitted and regular) for a queen size bed - works perfectly. We have used them on 5 trips of 1+ weeks each this summer. No problems at all. Take a couple of minutes to pack up in the morning. Fold it in thirds, crush out the air. Close the valves. Then roll it up like a normal foam mattress pad. When you get close to the end, open the valves and let the air out. Then repeat this process once more and they will slide right into their carrying bags.One note: DO NOT KEEP THEM IN THE STORAGE BAGS IF YOU ARE GOING UP IN ALTITUDE. Yes they will expand and then getting them out is difficult if not impossible. I use bungee cords to hold them closed when going up in elevation. I went from sea level to about 2500 or 3000 ft and had a tough time getting the pad out of the bag. However, I would never use another pad for camping. And no annoying air motor to inflate them. Just open em up and let them inflate. Before bedtime I put 5 - 10 lungfuls into it and it's perfect.
originally posted on mec.ca
I got this for a camp where I knew I was sleeping in a tent, it would get below zero at night and we'd be on wooden platforms. I have a really bad back due to injury so my old pre-injury 1/2" thick Thermarest wouldn't do anymore. I bit the bullet and got this guy and it is honestly the best purchase I have made in a while.I am a heavy person (215 lbs) and my hips didn't come lose to touching the ground, so I felt super cozy and supported. Since it's so thick, this for sure helped keep me warm at night (I was the only one who wasn't cold at camp; I was able to lend out my blanket to someone).It does take a good 5-10 mins to inflate, but that is well worth it for me to know I will be comfortable camping. It has its own bag you can carry it in, but this it not ... MoreI got this for a camp where I knew I was sleeping in a tent, it would get below zero at night and we'd be on wooden platforms. I have a really bad back due to injury so my old pre-injury 1/2" thick Thermarest wouldn't do anymore. I bit the bullet and got this guy and it is honestly the best purchase I have made in a while.I am a heavy person (215 lbs) and my hips didn't come lose to touching the ground, so I felt super cozy and supported. Since it's so thick, this for sure helped keep me warm at night (I was the only one who wasn't cold at camp; I was able to lend out my blanket to someone).It does take a good 5-10 mins to inflate, but that is well worth it for me to know I will be comfortable camping. It has its own bag you can carry it in, but this it not something you could bring trekking. But I don't do that so i'm not removing any stars for it, just thought I'd mention you can't compress it and it's quite large when rolled up. But again, don't care.It'll also work well if I have someone crash at my place, it's almost the size of a twin bed.
originally posted on mec.ca
We used to back country camp, then we got children, now, albeit temporarily, we are car campers. I got this mattress after reading a few of the reviews. OMG it is worth every penny. I still wake up in the night but not due to any hip discomfort or need to rollover or risk losing sensation in a limb for the rest of the day. In the morning... no stiffness...at all. It truly is amazing how much difference this mattress makes. My wife, who is even more back country than me has got mattress envy big time and after this weekends trip is breaking down and buying her own.An added benefit to this mattress is that we found we are able to get away with a lighter sleeping bag (due to the insulation from the ground) which offsets the bulk of this mattress a little bit.
| R-Value | 7.0 |
| Length | 203 cm |
Thermarest Mondoking 3D XXL Sleep Mat
Free delivery between 15–22 May
Thermarest Mondoking 3d Xx Large Sleep Mat
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
I've used lots of sleeping pads over the decades. As my wife and I are now 60, comfort while sleeping is more difficult to come by when camping. I bought two of these Mondo XLs and they are wonderful. Sleep as well as if I'm in my own bed.Put two of them together with sheets (fitted and regular) for a queen size bed - works perfectly. We have used them on 5 trips of 1+ weeks each this summer. No problems at all. Take a couple of minutes to pack up in the morning. Fold it in thirds, crush out the air. Close the valves. Then roll it up like a normal foam mattress pad. When you get close to the end, open the valves and let the air out. Then repeat this process once more and they will slide right into their carrying bags.One note: DO NOT KEEP THEM IN THE STORAGE ... MoreI've used lots of sleeping pads over the decades. As my wife and I are now 60, comfort while sleeping is more difficult to come by when camping. I bought two of these Mondo XLs and they are wonderful. Sleep as well as if I'm in my own bed.Put two of them together with sheets (fitted and regular) for a queen size bed - works perfectly. We have used them on 5 trips of 1+ weeks each this summer. No problems at all. Take a couple of minutes to pack up in the morning. Fold it in thirds, crush out the air. Close the valves. Then roll it up like a normal foam mattress pad. When you get close to the end, open the valves and let the air out. Then repeat this process once more and they will slide right into their carrying bags.One note: DO NOT KEEP THEM IN THE STORAGE BAGS IF YOU ARE GOING UP IN ALTITUDE. Yes they will expand and then getting them out is difficult if not impossible. I use bungee cords to hold them closed when going up in elevation. I went from sea level to about 2500 or 3000 ft and had a tough time getting the pad out of the bag. However, I would never use another pad for camping. And no annoying air motor to inflate them. Just open em up and let them inflate. Before bedtime I put 5 - 10 lungfuls into it and it's perfect.
I got this for a camp where I knew I was sleeping in a tent, it would get below zero at night and we'd be on wooden platforms. I have a really bad back due to injury so my old pre-injury 1/2" thick Thermarest wouldn't do anymore. I bit the bullet and got this guy and it is honestly the best purchase I have made in a while.I am a heavy person (215 lbs) and my hips didn't come lose to touching the ground, so I felt super cozy and supported. Since it's so thick, this for sure helped keep me warm at night (I was the only one who wasn't cold at camp; I was able to lend out my blanket to someone).It does take a good 5-10 mins to inflate, but that is well worth it for me to know I will be comfortable camping. It has its own bag you can carry it in, but this it not ... MoreI got this for a camp where I knew I was sleeping in a tent, it would get below zero at night and we'd be on wooden platforms. I have a really bad back due to injury so my old pre-injury 1/2" thick Thermarest wouldn't do anymore. I bit the bullet and got this guy and it is honestly the best purchase I have made in a while.I am a heavy person (215 lbs) and my hips didn't come lose to touching the ground, so I felt super cozy and supported. Since it's so thick, this for sure helped keep me warm at night (I was the only one who wasn't cold at camp; I was able to lend out my blanket to someone).It does take a good 5-10 mins to inflate, but that is well worth it for me to know I will be comfortable camping. It has its own bag you can carry it in, but this it not something you could bring trekking. But I don't do that so i'm not removing any stars for it, just thought I'd mention you can't compress it and it's quite large when rolled up. But again, don't care.It'll also work well if I have someone crash at my place, it's almost the size of a twin bed.
We used to back country camp, then we got children, now, albeit temporarily, we are car campers. I got this mattress after reading a few of the reviews. OMG it is worth every penny. I still wake up in the night but not due to any hip discomfort or need to rollover or risk losing sensation in a limb for the rest of the day. In the morning... no stiffness...at all. It truly is amazing how much difference this mattress makes. My wife, who is even more back country than me has got mattress envy big time and after this weekends trip is breaking down and buying her own.An added benefit to this mattress is that we found we are able to get away with a lighter sleeping bag (due to the insulation from the ground) which offsets the bulk of this mattress a little bit.
My 20 year old Therm-a-Rest got punctured, so I decided to replace it with maximum comfort in mind. The MondoKing 3D XXL is so roomy and comfortable you will forget you are sleeping in the woods. My old pad was a miracle in its time, but you always knew that one inch under your hip was hard ground. Not so with this one! However, there is a price. Rolled up dimensions are about 10"x30" and 6-8 pounds makes for a bulky package. Also, the deflating process will get your heart rate up. By folding and laying on the resulting lump you can push out a lot of air. You must next open it and start rolling from one end in order to get a tight enough roll to fit into the bag. While you are rolling at one end, the other end is busily re-inflating due to the expanding foam. With a ... MoreMy 20 year old Therm-a-Rest got punctured, so I decided to replace it with maximum comfort in mind. The MondoKing 3D XXL is so roomy and comfortable you will forget you are sleeping in the woods. My old pad was a miracle in its time, but you always knew that one inch under your hip was hard ground. Not so with this one! However, there is a price. Rolled up dimensions are about 10"x30" and 6-8 pounds makes for a bulky package. Also, the deflating process will get your heart rate up. By folding and laying on the resulting lump you can push out a lot of air. You must next open it and start rolling from one end in order to get a tight enough roll to fit into the bag. While you are rolling at one end, the other end is busily re-inflating due to the expanding foam. With a combination of tight rolling and body weight, you can roll it small enough. On my office floor it seemed easy, on the tent floor was a bit more work. You will want to store it inflated, so every trip will begin with a workout. If you can handle the storage and rolling process, you will never regret the purchase.
So nice I'd sleep on it at home (and have).Purchased this for car camping, and to reduce the use of my backpacking inflatable mattresses which are very prone to leaks.After setting up my tent, I just open the vents and toss it out.Going to sleep, just give it a few breaths and it's pretty much good!Used it for 2 years now and haven't had to worry about it leaking for a second.Pain/impossible to get back into its fabric bag, so I use a bungee cord around it to keep it secure for transport, much easier.Wouldn't knock a star off for that though, as the product itself is excellent.
Works best as a car camping/overlanding mattress. After purchasing the Mondo King XXL, I removed it from its bag, allowed it to self-inflate, and stored it that way for a week before it's first use. Self-inflation is now rapid and complete - I felt no need to add additional air.It is a very warm and comfortable mattress, and before I packed it up after its first use, I opened the valves while laying on it to simulate a puncture. I felt like it was still very comfortable that way and am not concerned about a puncture ruining my nights sleep. If it does ever get a puncture, I might not even bother trying to fix it until the trip was over.The only difficult part is deflating it and rolling it up. It basically requires grasping with both hands and resting both of ... MoreWorks best as a car camping/overlanding mattress. After purchasing the Mondo King XXL, I removed it from its bag, allowed it to self-inflate, and stored it that way for a week before it's first use. Self-inflation is now rapid and complete - I felt no need to add additional air.It is a very warm and comfortable mattress, and before I packed it up after its first use, I opened the valves while laying on it to simulate a puncture. I felt like it was still very comfortable that way and am not concerned about a puncture ruining my nights sleep. If it does ever get a puncture, I might not even bother trying to fix it until the trip was over.The only difficult part is deflating it and rolling it up. It basically requires grasping with both hands and resting both of your knees on the rolled up portion and slowly roll it up towards the open valves. I attribute that difficulty to its strong self-inflation characteristic, and it really wasn't that big of a deal, it's just slower/more difficult to roll up than a regular air mattress.I'm very satisfied with my purchase.
I’m not a small guy - 6’2”, 250lbs, so when my wife had some health issues and sleeping in the same bed became problematic, I went looking for an inflatable mattress to crash on until she recovered. We spent good cash on a few nice air mattresses - they all let me down, quite literally. Most couldn’t hold my weight, despite their claims, without losing air overnight after a couple months of daily use.On a lark I decided to look into camping mattresses as an alternative. After a bit of research on here, I landed on this one and have had a tremendous experience for months now. It takes a full day to fully inflate the first time, but once there, you close the valves and it holds its pressure, well...for months now. Yea...I’ve never had to reinflate it.It’s a bit ... MoreI’m not a small guy - 6’2”, 250lbs, so when my wife had some health issues and sleeping in the same bed became problematic, I went looking for an inflatable mattress to crash on until she recovered. We spent good cash on a few nice air mattresses - they all let me down, quite literally. Most couldn’t hold my weight, despite their claims, without losing air overnight after a couple months of daily use.On a lark I decided to look into camping mattresses as an alternative. After a bit of research on here, I landed on this one and have had a tremendous experience for months now. It takes a full day to fully inflate the first time, but once there, you close the valves and it holds its pressure, well...for months now. Yea...I’ve never had to reinflate it.It’s a bit less cushy than a traditional mattress, so that takes a tiny bit of adjustment (if you’re using it daily like I do) but despite my size, my butt never touches the ground and side sleeping is even comfortable. I would imagine that using this for camping would present a different set of needs than I’ve outline here, but if this can handle my daily use for months on end, I feel pretty confident recommending it for camping across the board.
This is a mixed review, and the low rating is exclusively for the nearly impossible task of trying to repack this mattress after using it. Good luck finding info on this, BTW. The size is great for sleeping, the R Value (11.4) is worth noting because we stayed free from ground coldness after a torrential 2 day rainfall with 40+ degree nighttime temps and the comfort level is unequaled...but... the storage size, even when we finally got them back into the sacks (after about an hour of total effort 2 separate times, no kidding it was tiring) makes it hard to recommend, and we are thinking very hard of returning them. They are large even in the sack and so, they take up a lot of room. The comfort value Vs. the limitations of use due to the size and weight i.e. cannot ... MoreThis is a mixed review, and the low rating is exclusively for the nearly impossible task of trying to repack this mattress after using it. Good luck finding info on this, BTW. The size is great for sleeping, the R Value (11.4) is worth noting because we stayed free from ground coldness after a torrential 2 day rainfall with 40+ degree nighttime temps and the comfort level is unequaled...but... the storage size, even when we finally got them back into the sacks (after about an hour of total effort 2 separate times, no kidding it was tiring) makes it hard to recommend, and we are thinking very hard of returning them. They are large even in the sack and so, they take up a lot of room. The comfort value Vs. the limitations of use due to the size and weight i.e. cannot be reasonably carried on a pack frame, make this mattress not very user-friendly. 3 Stars.
Got this for a bargain price at the annual garage sale. Tag said it was returned because the previous owner couldn't get it back in the bag. This is a common issue with this model but another reviewer figured it out. Open the valves and Roll the mattress pretty tightly, don't go nuts but try to get as much air out as possible. Once you have it rolled, close the valves and unroll the mattress. Now roll it again (keep the valves closed). It should be easier to get a tighter roll. Roll as tight as you can until you've squeezed whatever air is left into a pocket near the end. Open the valves and press out the last bit of air. Voila! Now it should fit snug but smoothly into the bag.This mattress is high Quality, great firmness and it holds all of its air. I sleep on my ... MoreGot this for a bargain price at the annual garage sale. Tag said it was returned because the previous owner couldn't get it back in the bag. This is a common issue with this model but another reviewer figured it out. Open the valves and Roll the mattress pretty tightly, don't go nuts but try to get as much air out as possible. Once you have it rolled, close the valves and unroll the mattress. Now roll it again (keep the valves closed). It should be easier to get a tighter roll. Roll as tight as you can until you've squeezed whatever air is left into a pocket near the end. Open the valves and press out the last bit of air. Voila! Now it should fit snug but smoothly into the bag.This mattress is high Quality, great firmness and it holds all of its air. I sleep on my side and it worked perfectly. Almost as good as home. Not good for hiking in or backpacking but if you're a car camper, get this mat.
Bought this after going through the both the rei camp bed 3.5 and mountain summit gear 3.5,. I returned both of those mats because they started leaking. I also went through 2 other 4 inch pads I bought off ebay. they all started leaking within a year or two. I decide to pay more for the thermarest name and am glad i did. The foam is softer and more comfortable than any of my previous car camping mats. I have thermarest mats i bought 20 years ago that never failed so I have great faith in the brand. I do take care of my mats all my previous leaks have been at the valves and delamintated seams not punctures from poor placement. Thermarest is made right here in the USA and backed by a solid warranty. I am confident this is the last mat I am going to buy. It did take 4 ... MoreBought this after going through the both the rei camp bed 3.5 and mountain summit gear 3.5,. I returned both of those mats because they started leaking. I also went through 2 other 4 inch pads I bought off ebay. they all started leaking within a year or two. I decide to pay more for the thermarest name and am glad i did. The foam is softer and more comfortable than any of my previous car camping mats. I have thermarest mats i bought 20 years ago that never failed so I have great faith in the brand. I do take care of my mats all my previous leaks have been at the valves and delamintated seams not punctures from poor placement. Thermarest is made right here in the USA and backed by a solid warranty. I am confident this is the last mat I am going to buy. It did take 4 days to inflate fully the first time but who know how long it was packed up for. Now it inflates much faster , just don't buy it the day before your trip and you should be fine
| R-Value | 7.0 |
| Length | 203 cm |
