The 23-year old defender has departed Bramall Lane to become Villa's third signing ahead of the 2012/13 season following Brett Holman and Karim El Ahmadi for a fee of £3million.
"It's every boy's childhood dream to play in the Premier League and it was one of mine," said Lowton who has been with the Blades since he was a youth.
"This opportunity is fantastic and I thank the manager for giving it to me. Hopefully I can repay the faith that's he's shown in me and keep going at a higher level.
"Just from driving up to the training ground you can see the difference in the quality of things. The training ground looks spectacular and the pitches look phenomenal.
"It's a massive club in the Premier League with a big fan base and I'm looking forward to getting to work as soon as I can."