An impressive game for Ralph Hassenhutl's side was dominated by several impressive and individual performances to cling on for a huge three points.
The first of those impressive performers being Che Adams who caught Ederson off his line in a sensational long-range effort 16 minutes into the fixture which was enough to seal the tie.
However, the victory was only achieved thanks to Saints withstanding relentless City attacks in part due to the incredible defending from Jack Stephens and goalkeeping from Alex McCarthy to see out the win.
Manchester City will no doubt come away disappointed having dominated possession at 74% and having 26 shots to Saints' six only a matter of days after slaughtering champions Liverpool.
Remarkable first goal
Che Adams' immense strike 16 minutes into the fixture was his first goal for Southampton in 30 matches, no doubt earning him the goal of the weekend and putting him in the running for Goal of the Month.
And what a goal it was to catch the Brazilian keeper off his line from such range and loop it over the shot-stopper, similar to Scott McTominay against Ederson earlier in the campaign.
It was certainly a remarkable goal to mark his first for the club following his £15million big-money move from Birmingham last summer. Was it worth the wait? Only Southampton fans can really answer that.
Manchester City have plenty of work to do
Pep Guardiola's side came fresh off of a 4-0 smashing at Liverpool's expense in midweek.
However, today showed if the Cityzens are serious about regaining the title next season they have plenty of work to do.
Despite dominating possession, shots, and just about everything other than the all-important stat in goals, the result showed their lack of ability to dispatch teams lower down the division and why they are 23 points behind the Reds.
While they do have the quality to overcome the big teams, as they did against the champions in midweek, it's against the sides lower down the division where they struggle and this is something that has to change if they are to have any chance of getting the title back next season.
Spectacular solo performances
As impressive as Adams' goal was for the South Coast side so was their defending all round.
To withstand as many attacks as they did is impressive in any Premier League game but especially against a side the calibre of Manchester City.
Former Reading, Crystal Palace, and QPR goalkeeper Alex McCarthy was an absolute rock in between the sticks and saved his side on many occasions, showing why he has earned himself number one spot under Hassenhutl.
Jack Stephens was another player who caught the eye, earning man of the match thanks to his incredible defensive shift at the back by getting his body in the way of just about every shot and blocking a few off the line too.
The defending really was that of a team defending for their lives in a relegation scrap not one set for midtable mediocrity - perhaps a sign of the changing times under Hassenhutl's reign.