Gomez, 24, has signed a three-year deal but no fee has been announced. He spent last season on loan with Martinez's former club Swansea City.
"Jordi is a real quality player. A great left foot and extremely pleasing on the eye as a player," Martinez told the club website.
Thank you for reading 5 articles this month* Join now for unlimited access
Enjoy your first month for just £1 / $1 / €1
*Read 5 free articles per month without a subscription
Join now for unlimited access
Try first month for just £1 / $1 / €1
MOST READ
