The 32-year-old's contract with Bayern is due to expire on June 30 and he is set to leave the club after arriving in 2012, having struggled for gametime during the 2020-21 campaign in an injury-hit season.
Martinez's time at Bayern has been decorated with silverware as he is a nine-time Bundesliga champion, five-time German Cup winner, four-time German Super Cup winner and two-time Champions League, FIFA Club World Cup and UEFA Super Cup champion.
According to Mundo Deportivo, Bilbao will make an offer to Martinez, who spent six years at the Spanish club between 2006 and 2012 before his £40m switch to the German giants.
The Spanish World Cup winner made 250 appearances for Athletic, scoring 25 goals during his spell at the San Mames, and he could return as the club have supposedly offered Martinez a two-year deal worth £2.5m per year.
Martinez has made 268 appearances for Bayern Munich in his nine seasons with the club and scored 14 goals from his defensive midfield position. body check tags ::