Thai Meethu Sathiyam (transl. I swear upon my mother) is a 1978 Indian Tamil-language Curry Western film directed by R. Thyagarajan and produced by Sandow M. M. A. Chinnappa Thevar. The film stars Rajinikanth and Sripriya, with Mohan Babu, Prabhakar, Suruli Rajan, Sundararajan, A. V. M. Rajan, S. A. Ashokan, Nagesh, Ambareesh, Jayamalini and Sukumari in supporting roles. It focuses on a shepherd who vows to avenge his parents by killing the murderers.

The film was originally planned by Thevar in the late 1960s under the title Marupiravi (transl. Rebirth) with M. G. Ramachandran intended to star; however, as Ramachandran was unwell at that time, as well as involved in a legal case, the film was shelved. Thevar later revived the project as Thai Meethu Sathiyam, with Rajinikanth cast in the lead role as Ramachandran had retired from acting by then. It was the last film produced by Thevar to be released; he died when the film was still in production.

Thai Meethu Sathiyam was released on 30 October 1978, a month after Thevar's death, and became a commercial success, running for over 100 days in theatres.