Match ends, Southampton 1, Crystal Palace 2.
Wilfried Zaha's second-half strike earned Crystal Palace a place in the FA Cup fourth round at the expense of Premier League rivals Southampton.
It was the second season running the Saints have lost to the Eagles who went in front when Joel Ward fired in from Jason Puncheon's pass.
Oriol Romeu slotted in the equaliser after Cuco Martina's effort was saved.
Zaha grabbed the winner when he volleyed in a loose ball after Puncheon's strike had been parried.
The Saints twice went close in the closing moments when Sadio Mane headed inches over before James Ward-Prowse's brilliant free-kick was tipped past the post by Wayne Hennessey.
Saturday's defeat means the South Coast side have now lost to the London club in the FA Cup in five of their last six meetings.
What's wrong with Southampton?
This is now seven defeats in their last nine games. As with some of their previous encounters, manager Ronald Koeman's men took control early in the match but then allowed the other side to get into their rhythm.
Some Saints fans might be at a loss to understand why their Dutch coach opted to start with a 5-3-2 formation against a side with only one man up front. His defensive approach meant that they barely created much at the other end.
Does he now need to throw caution to the wind?
Palace, who defeated Southampton in the league earlier this season, took the lead just before the half-hour mark when Ward - an ex Portsmouth player - struck home after good work from ex-Saint Puncheon.
Can the Eagles soar to cup success?
If they sustain this current from, then yes. It is now only one defeat in eight matches, and they sit within striking distance of a Premier League European spot.
Without midfield livewire Yannick Bolasie, manager Alan Pardew still has enough pace and guile in his attack to trouble most opponents. And at St Mary's Stadium Puncheon played a starring role.
The 29-year-old Croydon-born winger pulled the Saints defence one way and the other all afternoon. And having provided the assist for the first he also played a key role in the second.
After Romeu levelled for the home side, Puncheon drove forward and launched a fierce effort which Marten Stekelenburg could only push into the path of Zaha, who neatly tucked home.
The Eagles are a club to avoid in Monday's draw.
What the managers said
Palace boss Alan Pardew:
"There were some disappointing factors against Chelsea that were put right today.
"We had to lean on our tenacity and our defensive capabilities a bit more than I would have liked.
"This is what this team's about. We're difficult to score against with a good back four and goalkeeper. We can kill teams on the break.
"We're looking for a home draw, we don't really care who. With the fans we've got it's going to be tough for anyone."
Southampton manager Ronald Koeman:
"It's difficult to explain why we lost because I think we started well.
"We dominated the game and we had some good chances. Maybe we didn't make the right decisions with the final pass. We also made a big mistake in our ball possession.
"In the last 20 minutes we had some good shots on target.
"There was good goalkeeping from them. In football sometimes you are not so lucky and you have to accept that on one side."
The Saints host in-form Watford in midweek in the Premier League, while Palace are at struggling Aston Villa on Tuesday.
- 6José Fonte
- 17van Dijk
- 3YoshidaSubstituted forJuanmiat 45'minutes
- 4ClasieSubstituted forWard-Prowseat 76'minutes
- 8DavisSubstituted forTadicat 45'minutes
- 10ManéBooked at 82mins
- 7LongBooked at 86mins
- 2Cédric Soares
- 7CabayeSubstituted forJedinakat 83'minutes
- 28LedleyBooked at 90mins
- 9CampbellSubstituted forChamakhat 76'minutes
- 22MutchSubstituted forSakoat 57'minutes
- Lee Mason
- Shots on Target
Second Half ends, Southampton 1, Crystal Palace 2.
Corner, Southampton. Conceded by Wayne Hennessey.
Attempt saved. James Ward-Prowse (Southampton) right footed shot from outside the box is saved in the bottom right corner.
Joe Ledley (Crystal Palace) is shown the yellow card for a bad foul.
Sadio Mané (Southampton) wins a free kick in the attacking half.
Foul by Joe Ledley (Crystal Palace).
Attempt missed. Sadio Mané (Southampton) header from the centre of the box is just a bit too high. Assisted by Shane Long with a cross.
James Ward-Prowse (Southampton) wins a free kick in the defensive half.
Foul by Bakary Sako (Crystal Palace).
Delay over. They are ready to continue.
Delay in match Marouane Chamakh (Crystal Palace) because of an injury.
Shane Long (Southampton) hits the left post with a header from very close range. Assisted by James Ward-Prowse with a cross following a corner.
Corner, Southampton. Conceded by Damien Delaney.
Attempt blocked. Jose Fonte (Southampton) header from very close range is blocked. Assisted by James Ward-Prowse with a cross.
Corner, Southampton. Conceded by Damien Delaney.
Attempt missed. Oriol Romeu (Southampton) header from the centre of the box is close, but misses to the left.
Corner, Southampton. Conceded by Joel Ward.
Shane Long (Southampton) is shown the yellow card for a bad foul.
Foul by Shane Long (Southampton).