The 29-year-old frontman checked into Villa Park on Wednesday evening on a three-year deal for an undisclosed fee, understood to be in for an initial £25million.
The confirmation of the switch came totally out of the blue with Dean Smith already adding Leverkusen's Leon Bailey to his side's ranks earlier in the day, while skipper Jack Grealish is set to complete his £100m move to Manchester City in the next 24 hours.
Head coach Smith has wasted little time in powering his Villa frontline with more firepower, however, with experienced top flight frontman Ings – who scored 14 goals for club and country last term – added to the ranks.
The ex-Liverpool striker joins Bailey, Ashley Young and Emi Buendia through the door this summer.
Smith said: “Danny is an outstanding Premier League footballer who has scored goals wherever he has played.
"He is also a top professional with a great character who will be a leader in our squad and a role model for our rapidly developing young academy players who are now in and around the first team. I am delighted to welcome Danny to our great club."
Ings had just a year left on his Southampton deal and has previously been heavily linked to other Premier League moves, including to Tottenham.
Saints reacted to the signing following Villa's announcement of the deal by tweeting: "Southampton Football Club can confirm that it has accepted an offer from Aston Villa for striker Danny Ings."
Ings, who joined Southampton from Liverpool for £20m in 2019, reached the 100 career goals landmark last season. He scored 34 league goals in two seasons with the Saints.