England midfielder Ward-Prowse celebrated his 26th birthday in style with two brilliant free kicks at Villa Park to help lift the impressive Saints above Villa into third place.
The visitors could have scored more with Che Adams and Ings having goals ruled out for offside and Theo Walcott hitting the bar.
Tyrone Mings' header, Ollie Watkins' penalty and Jack Grealish's stoppage time goal gave the scoreline a flattering look for Villa.
After their 3-0 defeat to Leeds last time out, Villa's fine start to the season is now in danger of fading away.
They were second best from the start and the visitors thought they had opened the scoring after just three minutes when Ezri Konsa's clearance hit Adams to squirm in.
VAR took an age but eventually ruled the Southampton striker was marginally offside.
Walcott then clipped the bar from the edge of the area during a bright start.
The visitors were sharp and, while Bertrand Traore shot wide, Villa had no answer and were forced into an early change when Trezeguet replaced the injured Traore.
It made little difference to the game's dynamic though and Southampton got a deserved opener after 20 minutes.
Kyle Walker-Peters was fouled by Matt Targett and Ward-Prowse's excellent delivery was met by Vestergaard's thumping header.
Villa never recovered and the ruthless visitors went 2-0 up after 33 minutes.
Another rash challenge saw Douglas Luiz bring Walcott down 25 yards out and Ward-Prowse bent a brilliant free kick into the top corner.
It was Southampton's 1,000th Premier League goal and the skipper added the next just before the break.
Matty Cash was penalised for a reckless handball on the edge of the box and, while it was closer than his first, the result was the same as Ward-Prowse curled in.
Villa were poor but Southampton were outstanding and even when the hosts did carve out a chance soon after the restart, Alex McCarthy's saved Grealish's header.
But normal service resumed after 58 minutes as the previously quiet Ings finished off a flowing move when he cut in from the left and lashed in off the bar.
Villa pulled a goal back four minutes later when Southampton switched off for the first time, Mings glancing in Grealish's delivery after Stuart Armstrong lost possession.
Ings was denied a second by the linesman's flag before the hosts managed to close the gap late on.
They chipped away and McCarthy saved well from Trezeguet and Mings before he was beaten by Watkins' injury-time penalty after Ibrahima Diallo chopped down Grealish.
There was still time for the Villa skipper to add a third when he found the bottom corner from 18-yards.