The 27-year-old left-back joins the Baggies on a four-year deal and has elected to wear the No. 3 shirt.
Gibbs joins the Baggies after spending more than a decade at Arsenal – where he made over 200 appearances for the Gunners – and with ten England caps to his name.
But Kieran is now ready to embrace a new challenge. He says: “I watched the boys in the first few games of the season and they’ve got a lot of energy. They’ve made some good signings and I feel this is a good move for me.”
Albion Chairman John Williams says: “I’m delighted to welcome Kieran to the Club. We have recruited another quality addition, an England player with bags of experience at Premier League and Champions League level. We are confident he will do well for us.”