The Saints arrived at Wembley for the first time since the 2023/24 Championship playoff final, having already claimed Premier League scalps in Fulham and then-leaders Arsenal.
In their way stood the current top-flight table-toppers, who were contesting an eighth successive last-four meeting, making eight changes from their last outing.
That didn’t seem to affect City’s early rhythm, as they twice looked to get in behind, only to be denied by marginal Omar Marmoush offside calls.
The assistant’s flag took centre stage again during a busy opening quarter-hour, this time going up as Leo Scienza slotted home what he thought was the game’s opener at the other end.
Southampton were certainly holding their own in a competitive first half, but City were typically dominant in terms of possession and efforts, with Marmoush going close from a near-post shot that was smartly turned away by Daniel Peretz.
That proved to be the only effort on target for either side before the interval, meaning the Championship side failed to fire a shot of any kind before the break.
Maintaining their record of not conceding a first-half goal in the FA Cup this season, Southampton will have been pleased with the half-time stalemate, which almost served as a platform to take the lead were it not for a well-timed Nathan Ake recovery challenge to thwart Tom Fellows.
However, that wasn’t a sign of things to come, as Pep Guardiola made a double change before the hour mark, amping up the pressure on the Saints.
They remained defensively resolute, prompting further reinforcements in the shape of Erling Haaland and Nico O'Reilly, and soon after, they were hanging on when Peretz denied Gonzalez before Tijjani Reijnders volleyed wide.
Remarkably, after relentless attacks from City, it was Southampton fans who were in raptures 11 minutes from time when Finn Azaz collected the ball on the turn and bent an unstoppable effort beyond James Trafford with his second touch.
Unfortunately for those supporters, that lead lasted just four minutes, thanks to Jeremy Doku, whose arrowed strike took a notable deflection off James Bree that diverted the ball beyond Peretz.
Just four minutes later, Gonzalez found himself in space, arrowing in an effort from range that turned the tie on its head with little time remaining.
Southampton threw everything forward, surviving a counter-attack with a goalline clearance to deny Savinho, but there was ultimately no response, seeing City through to the final at their expense.
As a second division side, Southampton won this competition for the only time in 1975/76, but they won’t have the opportunity to do that again as focus shifts to the Championship promotion race.
As for Guardiola’s side, dreams of another domestic treble live on, with a final appearance against either Chelsea or Leeds United awaiting.
Flashscore Man of the Match: Nico Gonzalez (Manchester City)
