The England international has signed a four-year contract at The Hawthorns.
Speaking to the Albion club website, Gibbs said: “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.”
Club chairman John Williams said: “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.”
Although neither club has revealed the fee, it is believed to be in the region of £7m.
Sanchez
Gibbs spent 11 years at Arsenal, but it could be argued he never fully nailed down a first-team spot during his time at the club.
He enjoyed his most consistent run of form at the club when Gael Clichy was sold to Manchester City, keeping Brazilian Andre Santos out of the first team.
He will wear the No 3 shirt at Albion.
The 27-year-old also penned a heartfelt message on Twitter on completing his move.
West Brom have announced the signing of Kieran Gibbs from Arsenal for an undisclosed fee.
The 27-year-old has signed a four-year contract to become the Baggies’ latest summer recruit and follow Jay Rodriguez, Ahmed Hegazi, Gareth Barry, Yuning Zhang and Oliver Burke to the club.
Gibbs made over 200 appearances for Arsenal, but despite his early potential struggled to retain a regular place in Arsene Wenger’s starting XI and he is expected to be the first of several departures from the Emirates before Thursday’s transfer deadline.
I watched the boys in the first few games of the season and they’ve got a lot of energy,” Gibbs told West Brom’s official website. “They’ve made some good signings and I feel this is a good move for me.”
“Firstly I would like to say how delighted I am to sign for West Brom,” he added on social media. “It has been an amazing journey to play for my childhood club since I was 14.
“I would like to thank Arsene Wenger for giving me the chance to start my career and fulfil a dream.