AFC St Austell became the first Cornish side to reach the FA Vase semi-finals since 2007 as they came from 2-1 behind to beat Ascot United 3-2.
Martin Giles gave them an early lead in front of a club record crowd of 1,433, but Daryl McLean soon equalised and Damien Markman then put Ascot ahead.
Neil Slateford's strike drew St Austell level and top scorer Liam Eddy fired the winner three minutes later.
"I'm absolutely ecstatic," Eddy told BBC Radio Cornwall.
Eddy joined the club this summer having previously been a member of the last Cornish team to reach the last four of the FA Vase, Truro City, who won the trophy in 2007.
"I could not believe it, especially after the first half when we were behind," he continued.
"But we absolutely battered them in the second half, it could have been six or seven, especially if I could finish."
St Austell manager Phil Lafferty was impressed by the way his side bounced back after half-time against opponents two divisions above them in the English football pyramid.
"You won't find a prouder man this weekend, that's for sure," he said.
"I can't thank my players enough for believing and trusting at half-time that there was a way back into this game if we played to our opposition's weaknesses and our strengths, and boy did they in the second half.
"I'm proud, pleased, delighted and looking forward to Monday's draw."