Rein Oja (born February 26, 1956) is an Estonian actor, film director and theatre leader.

Rein Oja was born in Tallinn. He is the older brother of actor Tõnu Oja. In 1978 he graduated from Tallinn State Conservatory. In 1978-1997 he worked at Noorsooteater/Tallinn City Theatre. Since 1998 he is a freelancer