Engal Thanga Raja () is a 1973 Indian Tamil-language film, directed and produced by V. B. Rajendra Prasad. The film stars Sivaji Ganesan, Manjula, and Sowcar Janaki. It is a remake of the 1972 Telugu film Manavudu Danavudu, and loosely adapts the 1886 novel Strange Case of Dr Jekyll and Mr Hyde by Robert Louis Stevenson.
The film was launched at Vijaya Studios and a song was recorded on the same day. The songs were filmed at Ooty. Boopathi Raja, son of film's screenwriter Balamurugan portrayed the younger version of Ganesan's character.
The music was composed by K. V. Mahadevan, with lyrics by Kannadasan. The song "Iravukkum Pagalukkum" became hugely popular.
Kanthan of Kalki said the story was being driven by Janaki. The film ran for over 100 days in theatres.