The 30-year-old originally joined Sunderland on a season-long loan last summer but was recalled by the Cherries this month after the Black Cats found themselves in a relegation battle, and teams towards the other end of the Championship table - including Villa and leaders Wolverhampton Wanderers - expressed an interest in his signature.
The Villans have now won the race for the forward, who has previously earned promotion from the second tier with Norwich City and came close with Reading last term.
"It's a pleasure to be at a club like Aston Villa," he told the Villa website. "You only have to look at the stadium, the history and the support to know that this club deserves to be in the Premier League and hopefully I can play my part in getting this club back to where it belongs.
"It's an unbelievable squad of players here and they're on a great run of form as well so it's a great time to be joining."