Crystal Palace moved up to sixth in the table thanks to a Yohan Cabaye winner that inflicted a third defeat in four league games on struggling Southampton.
The hosts fully deserved their first Premier League win over Southampton, a victory that also extended Palace's unbeaten run to three league games.
Yannick Bolasie's perfect cross allowed the unmarked Cabaye to tap home from six yards late in the first half.
Southampton's best chance was a Shane Long strike late on.
Wayne Hennessey's stop to prevent the Republic of Ireland striker's low shot earning Southampton an injury-time equaliser was the Welshman's second outstanding save of the day - the first was an acrobatic reach to tip away the same player's goal-bound header when the match was goalless.
It ensured only Palace's fourth clean sheet in 24 home league matches, as the hosts held on for a win that moves them level on points with Tottenham, who are fifth on goal difference.