Galaxy S21 Ultra 5G • Locked AT&TBlack • 128 GB • Physical SIM + eSIM
(19 reviews)
$292.95
Save $913.86
Deals available
See limited deals and price drops
Free delivery by Jun 8 - 9
Express delivery by Jun 5 - 8 from $15.00
Deals available
See limited deals and price drops
All guaranteed 100% functional








Compatible charging cable

Refurbished price:$292.95
$1,206.81 newVersus $1,206.81 new
Battery
4.5/5
Shipping
4.5/5
Lens & Camera
4.7/5
Accessories
4.3/5
Packaging
4.5/5
Overall performance
4.1/5
Appearance
4.4/5
Reviewed 11/16/25, United States.
The device arrived in a timely manner in a condition and functionality stated in buy Back Market This is my second order using this site I also purchased an s22 ultra and have been very satisfied with both purchases
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Condition
Good
Purchased
11/2/25
Reviewed 11/10/24, United States.
Phone is perfect for me! So glad I could buy an ATT refurb, since some features are not available on unlocked devices. Replaced the same phone I had, an unlocked S21 Ultra with a cracked screen which would cost more to fix than this refurb, and since ATT service/reception has been going steadily downhill, really appreciate that I can use WiFi calling now. Yeah, I should switch but no guarantee that service would be any better. Totally happy with this purchase!
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Condition
Excellent
Purchased
10/31/24
Reviewed 8/14/23, United States.
I was honestly worried getting a used phone. But I wasn't paying 1000 for a phone. so I went back and worth for couple weeks and I had message company and asked few questions. They was awesome and answered all my questions. so I ordered the phone I wanted and it was here in 3 days. let me tell you. This phone looks brand new. I have had it for couple days and no problems at all. I absolutely love it. I will be buying more stuff from here.
Galaxy S21 Ultra 5G 256GB - Dark Gray - Locked AT&T
Galaxy S21 Ultra 5G 256GB - Dark Gray - Locked AT&T
Condition
Excellent
Purchased
8/8/23
Reviewed 10/17/24, United States.
The condition was near perfect though it had minor screen burn in only noticeable if you really look into it
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Condition
Fair
Purchased
10/15/24
Reviewed 3/5/24, United States.
This is my 3rd purchase from backmartket and I must say, they have never failed to deliver a quality product to me! This phone is in amazing condition it has 1 tiny little scuff on the screen that was maybe ⅛ of an inch long that was super shallow and completely disappeared when I put a screen protector on it!everything else works perfectly and it is a major improvement from my s10 thank your again backmartket I've recommended you to everyone that's said they needed a new phone and plan on purchasing all my tech from you in the foreseeable future if possible
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Condition
Excellent
Purchased
2/18/24
Reviewed 3/26/25, United States.
I got my device and the touch screen was either unresponsive or intermediate... so I got the label, the box and proofed of purchase... I sent it out 16th and got back to the seller on March 20th. so 2 business days would be the 21st, 24th, 25th, and 26th... with messaging back market waking what's going on the I get message back with that I believe is AI they are looking into it and never given me a direct answer just asking me to be patient... I'm losing wages with this problem as that's my works phone....
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Galaxy S21 Ultra 5G 128GB - Black - Locked AT&T
Condition
Fair
Purchased
2/26/25
Reviewed 10/31/24, United States.
I ordered an "excellent" condition phone for a little extra. The phone i got has scratches and dings on the metal body around the edges. Nothing to impair the use of the device, but one can't help feeling a bit ripped off. When you pay extra for condition, you expect to get what you pay for. Lesson learned on this one...
Galaxy S21 Ultra 5G 128GB - Silver - Locked AT&T
Galaxy S21 Ultra 5G 128GB - Silver - Locked AT&T
Condition
Excellent
Purchased
10/26/24
SM-G988MPN
128 GBStorage
Samsung Galaxy SSerie
0.71SAR head
0.99SAR body
SM-G998UManufacturer Ref.
Phantom BlackColor (official name)
2021Release Year
Dynamic AMOLED 2XScreen type
The Samsung Galaxy S21 Ultra 5G remains a powerful flagship smartphone despite being released in early 2021. It offers a large, vibrant display and a versatile camera system that caters to photography enthusiasts and heavy users alike.
Key features:The Galaxy S21 Ultra 5G is ideal for users seeking a premium Android experience with a focus on photography and multimedia consumption. It suits professionals, content creators, and tech enthusiasts who want a large, high-resolution display and advanced camera features. Compared to the Galaxy S22 Ultra, it offers similar core capabilities but lacks the built-in S Pen support and some software refinements.
Pros & Cons: Pros Cons High-resolution 108MP camera with versatile zoom options. Large and heavy design may not suit all users. Bright and smooth 120Hz AMOLED display for immersive viewing. Locked to AT&T network, limiting carrier flexibility. 5G connectivity for fast data speeds. No expandable storage option.Choosing a refurbished Samsung Galaxy S21 Ultra 5G supports sustainability by reducing electronic waste while providing a high-quality device. Each pre-owned phone is carefully tested and certified to meet Back Market’s standards for performance and reliability. Learn more about our quality standards.



The best prices for high-quality reborn tech by sellers we’ve checked and vetted. We don’t mind if you Google us.
Get to know us