Ings has signed a two-and-a-half-year contract as David Moyes searches for the goals to fire his side clear of a relegation scrap. The transfer fee could eventually rise to £15m including add-ons.
The paperwork was completed in time for Saturday’s crunch meeting with Everton.
The two sides are level on points in the relegation zone going into the crucial meeting, with both Moyes and Frank Lampard under huge pressure over their futures.
Moyes’ side have struggled badly for goals this term - with just 15 in 19 Premier League games - despite the £30.5million signing of Italian centre-forward Gianluca Scamacca in the summer.
Ings has scored six times in the League so far this season and was Villa’s top-scorer but had only started one game under new manager Unai Emery.
“For us, he was a very important player and his commitment was amazing. With me, he was so respectful,” Emery said yesterday.
"We decided on one offer from West Ham. The player was wishing to get it and I decided to let him go because for him it was a very good offer and for the club as well.”