Manager Tim Sherwood told Aston Villa's official website: "I'm really pleased to bring Jordan to the football club. He is a fantastic young player who is perfectly suited to the Premier League."
Ayew is the third player to swap France for Witton this summer with former Nice left-back Jordan Amavi and ex-Lille midfielder Idrissa Gueye already enlisted. Marseille-born forward Ayew - the brother of Swansea City winger Andre - scored 12 goals in 26 league appearances for Lorient last season and has earned 28 caps for Ghana.
In defence, Villa have recruited Micah Richards from Manchester City have also agreed a deal to sign 28-year-old full-back Jose Angel Crespo from Cordoba, according to the Spanish club.
Ayew insisted it took him just ten seconds to decide to move to Aston Villa. "When I spoke to the coach I knew this was the place for me," he said. "I didn't think twice. I knew he was the right coach for me.
"He has so much enthusiasm and determination for the game of football. It took ten seconds to work out he was the right coach for me and Aston Villa was the right team for me. I am the happiest man in the world. It's one of my greatest days in football.
"My dream was to play for a big team in England - and Aston Villa is undoubtedly one of the greats in English football."
Speaking about the English Premier League, Ayew continued: "It's the biggest in the world. That's why when the opportunity came, I didn't have to think twice.
"I know all about the Premier League because I have a big passion for football. I watched all the games when I was in France. I know all about the team and I know all the players by name."
Sherwood added: "I'm really pleased to bring Jordan to the football club. He is a fantastic young player who is perfectly suited to the Premier League."