Liam McAlinden's first-half goal earned promotion-chasing Morecambe a 1-0 win and saw Cheltenham drop to second in League Two at the Mazuma Stadium.
The striker was handed a rare start by Shrimps boss Derek Adams and made the most of his opportunity with a superb 20th-minute finish to maintain their promotion push.
A long ball forward was flicked on and McAlinden took the ball in his stride before providing a superb low finish to beat Scott Flinders from 12 yards out.
The home side thought they had doubled their advantage five minutes later when John O'Sullivan turned sharply in the box to fire home an Aaron Wildig cross, only to see the effort ruled out for offside.
After a sluggish start Cheltenham created a golden chance to level when Liam Sercombe's cross from the left gave Lewis Freestone a free header but he could only divert the ball over the bar.
The Robins had much the better of the play in the second half but were thwarted by some resolute defending from the home side.
Callum Wright went close with an effort tipped over by Kyle Letheran before he also volleyed over from close range, while Sam Smith fired inches wide in injury time after a smart turn and shot from the edge of the box as the Shrimps held on for the three points.