Ren Mar is a fictitious beach town in Southern California, implied to be a North County suburb of San Diego. It was home to Andy Botwin's Grandmother, whom they call Bubbe (Yiddish for grandmother), before she passed. The Botwin brothers, Judah and Andy, were brought up in Ren Mar. It is also the birthplace of Stevie Ray Botwin. Nancy, Andy, Silas and Shane relocate to Ren Mar at the start of season 4, and move into Bubbe's house, where Bubbe's caregiver, Andy's resentful father Lenny, also lives, until he moves out after discovering Nancy's side-business and starts blackmailing her.
A local Ren Mar teenager, Rad, remarks that whenever he swims in the ocean he gets a rash, alluding to the poor water quality near the San Diego-Tijuana border from industrial, agricultural, and sewage pollutants in the Tijuana River.
Locals believe that Ren Mar may represent Del Mar.