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Britax Marathon Convertible Car Seat Onyx
List Price: $279.99

Our Price: $239.99

You Save: $40.00 (14%)


Product Description

Keep little ones safe and comfortable during trips with this quality car seat that can be adjusted to two positions (rear- and forward-facing) depending on your child's development.


  • Rear-facing position holds up to 33 pounds; forward-facing holds up to 65 pounds
  • Patented Versa-Tether
  • Comfortably fits larger, older children
  • Removable, washable fabric cover
  • Patented HUGS system
  • Belly pad for comfort and protection
  • Built-in lock-offs
  • Sculpted base for a perfect fit
  • Flexible buckle LATCH system
  • Comfort foam and EPS protective foam
  • Tangle-free polyester 5-point harness
  • Belt holders keep belts aside for boarding
  • One hand recline adjustment

The Marathon from Britax is a durable, convertible car seat that helps keep your child safe and secure in the car. Ideal for parents seeking premium comfort and a higher, forward-facing harnessed weight capacity, the Marathon fits children rear facing from five to 35 pounds and children forward facing from at least one year old and 20 pounds, up to 65 pounds. Both positions can accommodate a standing height up to 49 inches.

The Britax Marathon offers:
  • HUGS system for maximum safety.
  • Easy-to-use push-button release LATCH connectors.
  • Five-point harness for a secure fit.

The Marathon's LATCH system is easy to adjust. (Crocodile color shown.) View larger.
An Easy-to-Adjust Design That Grows with Your Baby
The Marathon boasts an easy-to-manage design and enhanced features that can be safely used in cars with or without the LATCH (Lower Anchors and Tethers for Children) system. For one, it provides built-in lock-off clips that keep the seat tightly in place when using only traditional seatbelts at installation. Secondly, a simple handle pull allows the car seat base to be reclined when rear-facing, and soft padding and a stain resistant, removable and washable cover keep things cozy and stress-free.

In addition, the five-point harness system is made with strong polyester webbing, has tangle free straps, and fits snugly over your baby's shoulders, collarbone and hips to provide a secure fit. There are also four adjustable height positions so the seat can truly grow with your baby. Finally, the one-hand recline adjustment allows for proper positioning, which helps ensure your child's safety.

HUGS for Optimum Safety and Support
When it comes to safety, the Marathon truly delivers. First, the patented floating HUGS (Harness Ultra Guard) system exceeds U.S. safety standards by reducing forward head movement as it gently cushions the neck and chest with soft padding--a feature that's particularly important both in the case of an accident and during nap time. In addition, this system better distributes the webbing loads, reducing head movement and minimizing harness irritation on baby's neck in case of an impact. HUGS also reduces the chance of improperly positioning the chest clip.

Versa-Tether for Additional Security
Marathon also offers Britax's patented Versa-Tether, an anchor aid that provides additional security in the forward facing position for children weighing more than 50 pounds. The Versa-Tether fastens the top of the car seat to factory installed automobile anchor points, minimizing the possibility of a head injury in the event of impact. This system also allows for rear-facing tethering to help keep the seat consistently stable.

Weighing 16.5 pounds, and measuring 19.5 x 27.5 x 25.5 inches (WxHxD), the Marathon is also Federal Motor Vehicle Safety Standard (FMVSS) 213 compliant, meaning it adheres to a strict set of quality control and safety standards, and is approved for airline travel. The Marathon comes with a 1-year limited warranty.

The Marathon is also available in the following colors: Mariposa, Tan Swirl, Crocodile, Mossy Oak, All Star Blue, New Denim, Cowmooflage, and Granite.

  • 5 point harness with patented Floating HUGS system and 4 harness heights
  • Built-in lock-off clips, Versa-Tether & Safe Guard LATCH Connectors
  • EPS and Comfort Foam for safety and comfort
  • Rear- and forward-facing recline
  • Rear facing: 5 to 35 pounds. Forward facing: At least 1 year old and 20 to 65 pounds

Customer Reviews:

  • Britax Rocks!
    I love our new Britax marathon, I have always bought the cheaper carseats that the straps get all twisted so easily. They just feel and look cheap. This one is totally different. I love it! The only negative things I would say is that the bottom part of the harness (the buckle) should be out further a bit it has to be pulled out because it is under my sons rear-end and he is only 13months. I can't imagine buckling the bottom part with a child in cloth diapers. And the seatbelt that gets routed through rear facing is far too close to the bottom buckle as well, mine actually touches it, which I am sure doesnt help the first issue I mentioned. Also in the rear seating position it is hard to adjust the straps because the only way to pull to tighten it is up (vehicle seat is in the way)and that raises the lever so when you let go it just loosens again. But all in all it is a good carseat, although large. Barely fits rearfacing in my rear seat of my minivan (and only does in the middle of the bench seat), forward facing wouldn't be an issue but rearfacing the middle vehicle seat is too close on my van anyway! All that said I like the safety and durability and am buying another one soon for my daughter! But I may get another model (deathlon etc.) because she is bigger then my son. ...more info
  • Best Car Seat
    We have been extremely happy with our Britax Marathon. At first, it was tricky to put in the car. However, after the first time, it is fairly simple to get in and out of cars especially once forward facing. My daughter is in the 98% for height and the Britax accommodates her very well....more info
  • Great Convertible Car Seat
    Love everything about this car seat. It didn't take long to arrive; installation was easy; putting my baby in was easy too....more info
  • GREAT!!!
    I purchased this seat for my son one month before his first birthday. I wish that I had purchased it sooner. It was clear that his carrier seat was too small because his feet were hanging over. Now he has plenty of room and he actually looks comfortable. He seems so relaxed and enjoys facing forward. ...more info
    We are so happy with this purchase. We have a smaller car (corolla) and it still fits just fine. Our 8 month old son loves the seat too, which is most important! He seems very comfortable and falls asleep very easily. We like the recline on the seat versus some of the other convertables out there. It was pricey but turned out to be well worth the money as it seems like it will last and is so comfortable. ...more info
  • I will never buy another car seat
    This car seat is beyond perfection. I cannot relate to people who have any complaints to make. It takes about 2 seconds to install with the latch system. I sit in it and wiggle from side to side until it doesn't budge. Everything about it meets the needs of any other standard car seat, this one is just better quality overall. I will never buy another brand of car seats. ...more info
  • Safety First
    I bought this product for my grandson because the reviews I'd read said it was one of the safest car seats. It came in a bashed up box, but the seat was in good shape. It needed to be rear facing so it was difficult to install tightly so we brought it to our fire department to have it installed. He also told us it was one of the safest seats out there. I'd highly recommend the seat and also professional installation. A safe seat doesn't work properly if not installed correctly....more info
  • A matter of choice
    My Britax is 4 years old now and on it's 2nd child. It's great because the cover is removable unlike other brands, the straps pull easily and secure. This is easy to install whether you have the latch system or not, though the latch system is a heck of a lot easier than the old fashioned way of manuevering that metal clip. However, the harness covers are now tearing. This is my only complaint about this seat.
    I would recommend this because when you buy a car seat you are investing in your child's safety and the fact that this seat goes up to 65 pounds, saves you the aggravation of buying a new seat every 20 pounds....more info
  • Britax Marathon Car Seat
    This car seat is really great for both safety and comfort. I feel that my child is very well protected and she definitely enjoys the cushy seat. Seat was very easy to install as long as you have LATCH in your car. The only reason I wouldn't give it 5 stars is because the owner's manual was a little hard to interpret. I would assume that any person who had never used the LATCH system would have a lot of trouble trying to figure out how to install the seat just by looking through the owner's manual (luckily Britax uses the exact same mechanism that my infant seat did). This is kind of a major flaw since there are such a huge percentage of car seats that are not installed correctly.

    So, take advantage of the free services the Fire/Police dept.'s offer and just get the seat checked out before use because this is otherwise an outstanding product. ...more info
  • Great
    I just bought the second one for my second son.
    My elder son has been using it for 1.5 years.
    Love the New Denim material. Much cooler then other materials.
    My sons get hot easily in California weather.
    He always sweet in his old carseat.
    The new Denim is much better.
    Marathon is easy to install.
    Just to remember that it is a hugh seat.
    Better try it out in rear-facing position before you buy.
    I have to move the front seat a bit to forward to accomodate it.
    Luckily, I just need to do it for a few short months, then my son can use it forward-facing....more info
  • i love it!
    i bought for my 7 month old daughter and i have to say ...i didnt belive what a diffrent would make this carseat. we had diffrent ones befor and she always was crying and moving arround as soon you put her in the old one and didnt stop until i took her out:( in the new one she dont wont to go in there either but as soon she is in thre she is quite and plays with her toys until she is asleep.i love it!!!...more info
  • Car Seat
    So far I really like this car seat. My son really loves to sit in it. Easy to strap on the baby and seems very comfortable. ...more info
  • Love this carseat
    We have purchased a britax carseat before and were very pleased. We also have a graco carseat. We decided to go with another britax carseat for our smallest child as well even though they are a little more expensive. However, you get what you pay for. The britax allows for our children to take naps in the car without their head falling forward. It gives them very good support for their head and body. This particular carseat has strap covers that go on either side of the neck that work perfectly to protect from the straps cutting into your child's neck. It is a little harder to handle than other carseats because it is so bulky, however, it is worth the extra effort...more info
  • very well made product
    This is an awesome car seat. The only reason I am not giving it 5 stars is b/c the cover isn't completely suitable for hot weather. It's sort of like fleece, which makes it really hot in the summer for the baby who still has to face back. If there is an option to choose a cover that isn't fuzzy, I recommend that one if you live in a hot climate....more info
  • I love the Cowmooflage!
    This carseat is fantastic! I already had the Marathon in the Platinum pattern, but we needed a second carseat. The Cowmooflage is so soft and super cute. We have one Marathon installed with LATCH and one installed with a lap only belt, both rear facing, and both ways are very easy to install properly. I love that Britax makes the built in lock-off for the car belt. No need to use one of an "H" clip to lock the belt. Also, the Versa Tether is very handy. Both of our seats are tethered.

    Britax makes safe seats, and I love that the Marathon has high rear facing and forward facing weight and height limits. My daughter is 26 months old, and we still have her rear facing. If you don't already know about the benefits of extended rear facing, please check it out. It's so much safer than forward facing. And please know that the 1 year and 20 lbs. is just the minimum for forward facing, and that doesn't mean that they have to forward face at that time....more info
  • Very girly and lively print
    Excellent quality seat. This particular print is beautiful. I bought the seat for my younger one but I now had to order just the cover from Britax coz now my older daughter wanted the same cover. It is lovely....more info
  • A++
    I bought this product for my 6 month old daughter, and the cow print for me!! After hearing great things about this seat from people. And all the positive reviews, i was won over! At the moment i still have the seat rear facing so i haven't saved anymore more room than i had with her carry seat! However it was easier to install and seems a lot more secure than the Car seat i had with my travel system. I love it so much, i'm going to buy another one for my husbands car too!! A++...more info
  • Britax Marathon Convertible Car Seat
    I bought this car seat for my daughter. She just loves it. She found it well padded and sturdy. I would definitley recommend this to anyone looking for a quality car seat....more info
  • Great car seat!!
    Love this car seat. It is a top rated car seat and Amazon offered the best deal. It was easy to install and the product's reputation is A++....more info
  • Big, Sturdy, Safe Seat
    We were very impressed with this car seat. It gives you several installation options and it was quick and easy to install. All of the buckles and straps operate smoothly and once it is installed it is rock solid. We paid a little extra to have this seat but it is also built well enough that it should last us for several more years/ children. I would highly recommend this seat to others. ...more info
  • best car seat
    This is my second Britax Marathon. I bought one for my son 2 yrs ago. My daughter is 14 mo and we "upgraded" her from her Graco 2 months ago. We are still practicing extended (after a yr) rear facing for additional safety and it works out fabulous. So much room to just set her in and buckle her in. Now she can see her brother ( who is 3.5) who faces forward. The only thing is I would like to expand my family, but that would mean getting a bigger vehicle. I drive a Ford Escape and only 2 Britax will fit in the back. I think it is a combo of thecar seats being bigger and me having a smaller SUV. I would glady buy a new vehicle to keep my Britax. My husband has an Eddie Bauer and a Britax type knock off by Graco. Does not compare!!!So worth the extra cost. The pounds you can use it up to are higher than the ones my husband has thus extending their life...more info
  • Comfortable and safe
    This car seat has a lot of padding and my baby seems very comfortable in it. Overall the material and construction of this seat is very good. I have been using it for ~5 months. I feel safe to put my baby in it.

    One thing I really like is that this seat can hold a toddler up to 65lbs. So I probably don't need to buy a booster seat in the future.

    When I first install this car seat, I spent over half an hour but couldn't find the latches. I thought it was missing and was about to return it, then I found it under the seat cover. You have to read instruction very carefully to find out where it is. If you cannot the latches either, look at their video instructions online.

    I like this car seat and I'll give it 5 stars. However, there are a few you may want to know:
    - there seems to be a lot of color selections but they don't look attractive at all, at least to me.
    - when I installed this seat facing backward to my SUV, it totally blocked the view of the rear-right windows (I installed it to the back seat on the right). I felt very uncomfortable when cutting lanes. I had to move the front passenger seat all the way to the front so that I can still see part of that window. Of course I couldn't use the front passenger seat in the last few months....more info
  • Britax Marathon
    I was totally estatic when I did a search for a Britax Marathon and found this! After purchasing the same car seat for my son almost two years ago, I was dreading the idea of spending another $300 on a car seat. Ater doing research on different car seats, I couldn't bring myself to purchase something other than a Britax. So I checked out the Amazon website and found this hot baby for $192--a closeout! How lucky is that?! Its a great seat, I know how to install it, and most of all I'm comfortable knowing my daughter is safe in it. ...more info
  • Saved our road trip!
    My one year-old was SO comfortable in this seat on our cross-country road trip this winter. It reclines easily while attached, the fabric is comfortable and cushy, and it's BIG. The size may be a disadvantage to some people, but we did not have a problem fitting it in our Toyota Corolla in either rear or front-facing positions.

    One small complaint: the seat is annoying to strap in rear-facing position, but very easy to do in front-facing. If you have to move it from car to car at all, that would be a minor hassle....more info
  • Best car seat out there
    We bought 2 of these for our daughter so we would have one for both our cars. I moved her into it when she was about 8 months old because although she was still in the weight limit of her infant seat, she wasn't comfortable anymore. It was easy to install with LATCH in our vehicles. Our daughter loves this seat! She is so comfortable. She is 21 pounds at 13 months but we still have her rear-facing and will keep her that way until she reaches the limits. She is still comfy. She falls asleep or plays happily in her seat. I am confident that she will be comfortable on our long road trips we have planned this summer. Plus I love the patterns they have for girls! I wish they had more patterns for boys because I will be buying this seat for our next child as well. We have the Brooke in my car and Mariposa in my husbands. We have another car seat (Graco Comfor Sport) for the nanny and it is not as cushy and comfortable but she doesn't ride in it often/ ...more info
  • Great Car Seat
    This is a great car seat. Our son, at the time was 3 month (who is now 19 months), needed a better car seat that could accommodate his growing. After months of research, we decided on this one. I like the fact that it can hold a baby that grows fast in a rear-facing position. Our son, when he hit 3 months started growning like a weed, and he hates the car and we were hoping that this car seat would fix the problem. After a couple months in this car seat, he still didn't like the car... Even after he hit 1 and was foward facing. The car rides were more enjoyable with this car seat because of how high it sits up. He likes the fact that he can look out the window. Now, even though we spent all that money on this car seat, he ended up picking his own car seat and he liked the Graco Nautilus. I hate to spend more money on a car seat with only having this one for a little over a year, but if our son is going to be happy, it doesn't matter. We can put this one in my car so that we don't have to keep moving them. We told all of our friends and family that have little ones or are going to be having babies to buy this seat. I like the fact of how safe it is. ...more info
  • Best Car Seat Ever!!!
    This is by far the best and easiest car seat to use. It took me only 5 minutes or less to secure the seat to the anchors. The narrow seat base fits perfectly in the middle 2nd row seat of our Lexus GX470. It locks down tight and does slip/move at all. My 16 month old daughter loves this seat. Highly recommend this car seat. Excellent quality and value. The Cosco Omega series doesn't even come close to this Britax car seat. The only insignificant con is that it didn't come with a cup holder....more info