Martinez is out of contract in June 2021 and there has been speculation about a departure this summer.
Rennes can offer Martinez an ambitious project that involves playing in the Champions League.
The Spain international has been a big hit at Bayern since arriving from Athletic Bilbao in 2012.
Despite suffering many injuries, Martinez has played a big part in the Bavarians’ success, including the 2013 Champions League win.
Rennes have already recruited Martin Terrier this summer, paying Lyon €12m for the attacker.