United went into the game knowing they needed to better Tranmere's result to give themselves a chance of taking their survival fight to the final day of the season.
United's defeat coupled with Tranmere's victory over Crewe means that United are relegated to the National League.
Mark Hughes made one change to the startling line-up, with Matty Dennis returning from suspension to replace Joe Hugill. Paul Dummett returned to the bench following his spell on the sidelines through injury.
The home side started the game as the stronger side as United had to deal with balls into their box, but it was the Blues who had the first real sight of goal. Kadeem Harris got on the end of a Georgie Kelly flick but he could only drag the shot wide.
Georgie Kelly was the next player to have a chance on goal. Stephen Wearne did well to get the ball into the box but the striker had to reach to get on the end of it and sent the effort over the bar.
Cheltenham created their first chance of the game with 17 minutes on the clock. Ryan Haynes got the ball into the box from the left and Ashley Hay met it on the volley. Gabe Breeze was there to produce a fine stop to push it away for a corner.
Georgie Kelly forced a save out of Joe Day in the home goal after he took a left footed shot from the edge of the box, and Cheltenham cleared the danger from the resultant corner.
Matty Dennis put United ahead with half an hour played. Aaron Hayden's ball forward was ficked on by Stephen Wearne to send the striker through on goal. He kept his calm and slotted home.
Two minutes later, Cheltenham were awarded a penalty when Gabe Breeze was judged to have taken down his man. The United keeper was booked and Jordan Thomas sent him the wrong way from the spot to even the scores.
The Blues had the chance to go ahead just before the break when Matty Dennis was played through by Stephen Wearne again. The striker's touch took him wide and he sliced the shot over the bar.
The hosts took the lead on the stroke of half time when Ashley Hay got on the end of a ball forward to lift it over Breeze in the United goal.
HALF-TIME: Cheltenham 2-1 United
United started the second half strongly and had shouts for a penalty of their own when Georgie Kelly went down in the box, but the referee wasn't interested.
Ethon Archer had a sight of goal for the hosts with an hour gone, but his curling effort from the edge of the box hit the roof of the stand behind Breeze's goal.
Cheltenham should have scored their third goal with 65 minutes played, but Stubbs fired the shot over the bar after Jude-Boyd had found him in the box.
United got themselves level with another goal from Georgie Kelly. Elliot Embleton put a great ball into the box and the striker was there at the back post to head home.
The Blues created another chance shortly after the goal when Kelly found Dennis in the box, but a Cheltenham man got back to make an important tackle.
From the resultant corner, Embleton got another dangerous ball into the box but Georgie Kelly could only head this one wide.
George Miller got the winner for the hosts in added time when he fired past Gabe Breeze from the edge of the box.
FULL-TIME: Cheltenham 3-2 United
Teams:
Cheltenham - Day, Jude-Boyd, Haynes (Power 59), Kinsella, Bradbury (Bakare 78), Hay (Taylor 78), Dulson (Miller 59), Thomas, Archer, Stubbs, Backwell (Dieng (59).
Unused subs - Diallo, Williams.
United - Breeze, Harper (Dummett 79), Thomas ©, Hayden, Kelly, Ellis (Vela 67), Dennis, Wearne (Embleton 67), Harris, Whelan, Fusire (Hugill 79).
Unused subs - Lewis, Barclay, Bevan.
Goals:
Cheltenham - Thomas (33), Hay (45), Miller (93)
United - Dennis (29), Kelly (73)
Yellow cards:
Cheltenham - Jude-Boyd (82)
United - Dennis (6), Breeze (32), Hayden (32)
Red cards:
Cheltenham - N/A
United - N/A
Match officials:
Referee - Tom Nield
Assistant Referee - Bhupinder Singh Gill
Assistant Referee - Greg Read
Fourth Official - Oliver Nolan
Attendance:
4,963
