The 25-year-old defender, a product of the club’s academy, was handed the deal after establishing himself as key member of the first-team squad.
The Republic of Ireland international, who had been linked with a move to city rivals West Brom, admits signing a new contract is a huge personal boost ahead of the new Premier League season.
“I’m absolutely thrilled,” he told Villa’s official website. “I’ve been at Aston Villa since I was a kid and I want to continue to play for this fantastic football club.
“Everyone is looking forward to the new season and I’m delighted to be going into the opening game on Saturday knowing my long-term future has been sorted.”
Villa manager Tim Sherwood was equally happy with Clark’s decision, adding: “It’s great news.
“Ciaran wears his heart on his sleeve. He was unfortunate with injuries last season but he looks sharp now and we want to keep him fit.
“You know what you’re going to get from Ciaran. He gives everything for the cause and that’s all you can ask for as a manager. We’re pleased to have him here for a longer time.”