The 29-year-old completed a return to the Premier League having been relegated with Reading at the end of the last campaign.
Kebe ends a five-year spell at the Madejski Stadium which has seen two Premier League campaigns, a promotion and two relegations.
He had not featured in Nigel Adkins' side's opening five games of the Championship season and admitted he was delighted to return to the top flight.
"It's a big move for me," he told the club's official website. "I didn't know if I was going to be able to move in this transfer window but getting back to the Premier League was my main target. I'm very excited about it.
"I talked to the manager (Ian Holloway) and you can see how excited he is and I'm ready for the challenge.
"It's a big opportunity for the club and we know it's not going to be easy to stay in this league as there's a lot of good clubs but anything is possible, so we'll try our best.
"I was in the same situation with Reading and it's never easy to move from the Championship to the Premier League as it's a big step but there's quality players here and we have a strong team to do something with here.”
Kebe made 18 appearances in the league last season scoring five goals.
