Clarkson, Hammond and May now present a rival motoring programme, The Grand Tour, for online streaming service Amazon Prime.
After Evans quit Top Gear after just one series, amid falling viewing figures, LeBlanc became the new face of the programme, supported by racing driver Chris Harris and journalist Rory Reid.
"Matt has thrown himself into the show with real passion, revealing his extraordinary car knowledge and a willingness to get down and dirty," BBC Two controller Patrick Holland said.
"We were always going to be borrowing him from his day job as one of the top comic actors in Hollywood so I wish him all the very best."
Alongside Top Gear, the actor currently stars in two US sitcoms, Episodes and Man with a Plan.
No replacement for LeBlanc has been announced, but Holland said the producers "have great plans to welcome a new co-host to join the team for 2019 and beyond."
LeBlanc is divorced, but retains joint custody of his teenage daughter he had with his first wife, model Melissa McKnight. In 2016, he said he sees parenting as the most important part of his life.
"I remember when my daughter, Marina, was born. The second I laid eyes on her, I was in love," he said. "Spending time with her is the best thing I've ever done. We have a great bond and it's the best thing in my life."
