The prolific 26-year-old joined Sunderland for an initial 10 million pounds from Tottenham Hotspur in 2009 and the total fee for his latest move could rise to 24 million.
Villa's previous record was the 12 million-pound deals that brought James Milner and Stewart Downing to Villa Park.
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Bent signed a four-and-a-half year contract and could make his debut in Saturday's home game against Manchester City, the Premier League club said in a statement on their website.
Bent, who began his career with Ipswich Town, scored 25 goals in his first season at Sunderland and has netted 11 tin the current campaign. He has one goal from his seven England appearances, most as a substitute.
"Aston Villa is a massive football club and as soon as I knew they were interested in signing me I wanted to join," Bent told AVTV.
"The size of the football club and the history of the club are major reasons for me coming here.
"There are some top, top players here too, real quality, and I've been able to speak to the manager and the owner about their ambitions for the club."
TRANSFER FUNDS
The signing will delight manager Gerard Houllier, under pressure with his side above the relegation zone only on goal difference, but may vex former boss Martin O'Neill who left before the season started after becoming frustrated by lack of transfer funds.
Sunderland manager Steve Bruce, whose team are flying high in sixth place, was not happy either having taken Bent to the north east following an unhappy spell at Spurs.
"It's hugely disappointing that Darren has decided that his future lies away from Sunderland and the players, our supporters and the club as a whole have every right to feel massively let down," he told the club's website.
"The timing is especially hard to take, given that we are progressing positively and are in a great position to push on.
"Everyone has been nothing but supportive of Darren in his time at Sunderland but it's obvious he's not been himself in training and we've certainly not seen the best of him in games in recent weeks. We now understand why.
"I've always stated that my aim is to build a talented, young squad for the long-term to help the club achieve sustained success and I want Sunderland fans to know that our ambitions haven't changed on that front."
