The 35-year-old center back reunites with his former Liverpool coach at the Scottish champion, having signed a one-year deal after his release from the Reds.
Celtic has announced the signing of Kolo Toure on a one-year deal.
The 35-year-old rejoins forces with Brendan Rodgers, under whom the Ivory Coast international played during his time at Liverpool.
Rodgers replaced Ronny Deila at the helm of the Scottish champion this summer and has already snapped up Moussa Dembele in the current window, with Toure, who had been released from Liverpool, the latest addition.
The Northern Irishman was delighted to team up with the former Arsenal and Manchester City player once again.