Chelsea captain Cesar Azpilicueta brought down Stuart Armstrong just outside the area in the 45th minute and Ward-Prowse curled a free kick over the wall into the right-hand side of the net with goalkeeper Kepa left sprawling.
Chelsea FC 0-1 Southampton highlights as Ward-Prowse scored
Azpilicueta needed nearly 10 minutes of treatment on the pitch in the second half after he received a kick to the head in a goalmouth clash. Physios from both clubs rushed to his aid and the Spaniard was eventually carried off on a stretcher.
Chelsea, who have scored only four goals in 10 games in all competitions since the start of the year, looked livelier in the second half when Raheem Sterling and Kai Havertz came on and they kept the Southampton defence under pressure.
But despite spending nearly 300 million pounds ($361.05 million) in the January transfer window, the Blues still could not score against the south-coast team led by caretaker coach Ruben Selles after Nathan Jones was sacked a week ago.
Chelsea are languishing in 10th place on 31 points from 23 games and are 10 points adrift of the top four. Southampton have 18 points and are three points outside the safety zone.
