Match ends, Cheltenham Town 0, Dover Athletic 1.
Conference side Dover progressed to the FA Cup third round for the second time in four years after beating Cheltenham.
Defender and captain Connor Essam finally broke the deadlock in the 83rd minute when he struck low past goalkeeper Trevor Carson.
Earlier in the game, home striker Terry Gornell's header was disallowed after the ball rolled marginally out of play.
The League Two side failed to respond to Essam's late strike, which was no more than the non-league side deserved.
Although they came into the game as underdogs, Dover were on a 10-game unbeaten run and had already seen off League Two Morecambe in the first round.
The Whites were looking to repeat their exploits of their cup run in 2010-2011, when they beat Aldershot to reach the third round for the first time in their history.
And they impressed against a Cheltenham side who are 17th in League Two and still in transition after the appointment of new manager Paul Buckle last month.
Dover looked intent on causing an upset in the first 15 minutes, but Nick Deverdics' lob and Tom Murphy's effort were both stopped by Carson.
As their bright start began to fade, Cheltenham pushed forward and Gornell's sliding shot deflected off Essam and round the post.
Gornell was then denied an opener by referee Dean Whitestone, who ruled out his header after the cross from Kane Ferdinand was touched out of play by a Dover defender.
It remained evenly poised in the second-half, as Tom Bonner lashed over for Dover after a goalmouth scramble and Cheltenham's Jason Taylor put two low shots carelessly wide.
The visitors gained momentum in the final stages and just after defender Richard Orlu had struck off the woodwork, Essam pounced to send Dover through to the third round.
Cheltenham Town manager Paul Buckle told BBC Sport:
"We had enough chances in the game, in really good areas, to slam the ball in the back of the net.
"The only real bit of quality in the game is when the boy spun and smashed it into the bottom corner.
"We've only got ourselves to blame. I wish Dover all the best - they deserved the win.
"We have got a lot of work to do. We needed to score today, it was a really even game and a golden opportunity for us to be in the third round. I'm deeply disappointed that we couldn't at least draw the game and take it to a replay."
- 28De VitaSubstituted forKotwicaat 90+1'minutes
- 10GornellBooked at 87minsSubstituted forWilliamsat 88'minutes
- 18DaviesSubstituted forWynterat 40'minutes
- Dean Whitestone
- Shots on Target
Second Half ends, Cheltenham Town 0, Dover Athletic 1.
Substitution, Cheltenham Town. Zack Kotwica replaces Raffaele De Vita.
Substitution, Cheltenham Town. Harry Williams replaces Terry Gornell.
Terry Gornell (Cheltenham Town) is shown the yellow card.
Foul by Matt Richards (Cheltenham Town).
Tom Bonner (Dover Athletic) wins a free kick in the attacking half.
Jason Taylor (Cheltenham Town) wins a free kick in the attacking half.
Foul by Tom Wynter (Dover Athletic).
Attempt missed. Tom Murphy (Dover Athletic) right footed shot from long range on the right is just a bit too high.
Goal! Cheltenham Town 0, Dover Athletic 1. Connor Essam (Dover Athletic) right footed shot from the centre of the box to the bottom left corner. Assisted by Tyrone Sterling.
Corner, Dover Athletic. Conceded by Jason Taylor.
Tyrone Sterling (Dover Athletic) hits the right post with a left footed shot from the left side of the box.
Attempt saved. Tom Murphy (Dover Athletic) right footed shot from outside the box is saved in the top centre of the goal.
Attempt saved. Craig Braham-Barrett (Cheltenham Town) right footed shot from a difficult angle on the left is saved in the centre of the goal.
Attempt missed. Jason Taylor (Cheltenham Town) right footed shot from the centre of the box misses to the left.
Attempt missed. Jason Taylor (Cheltenham Town) right footed shot from outside the box misses to the left.
Attempt saved. Raffaele De Vita (Cheltenham Town) right footed shot from the left side of the box is saved in the top right corner.
Tom Wynter (Dover Athletic) wins a free kick in the attacking half.
Foul by Raffaele De Vita (Cheltenham Town).