West Brom acquired winger Serge Gnabry from Arsenal on a season-long loan on Friday.
Gnabry, 20, had his medical this week and will wear No. 31 for the Baggies.
"I'm very delighted by the move," Gnabry told West Brom's website. "I see the opportunity that I can play, it's a good club and I've heard good things.
"I'm very happy that I've signed here. I've got good impressions and I feel it's a good environment for me to play and also develop as a player."
NEW SIGNING: Albion are delighted to announce the season-long loan signing of @SergeGnabry from @Arsenal #WBA #Gnabry pic.twitter.com/nidVE62RXf
- West Bromwich Albion (@WBAFCofficial) August 7, 2015
West Brom coach Tony Pulis said the Germany under-21 international will provide depth in the midfield.
"We're delighted to add Serge to our options," Pulis said. "He is a top player and he will bring us quality in certain areas of the pitch."
Gnabry joined Arsenal in 2011 from his hometown club Stuttgart and has made 19 appearances for the Gunners.
He joins James McClean, James Chester and Rickie Lambert as new signings at The Hawthorns this summer.