Massu Engira Masilamani (transl. Masss alias Masilamani; previously titled as Masss) or simply known as Massu is a 2015 Indian Tamil-language action horror comedy film directed by Venkat Prabhu, who co-wrote the script with Madhan Karky. It was produced by K. E. Gnanavel Raja's Studio Green and Aadnah Arts. The film stars Suriya in dual roles, alongside Nayanthara, Pranitha Subhash, Premgi, Parthiban, and Samuthirakani. It follows Masss, a con artist, who starts interacting with ghosts. During one such encounter, he stumbles upon Shakthi, a ghost who wants to seek revenge against his family's killers.

The film was launched in April 2014, and the principal photography commenced in July 2014 and was completed in April 2015. Filming took place in various locations in India and Bulgaria. The film's title Masss, was announced in July 2014; however, in order to receive exemption from entertainment tax, the film's title was changed to Massu Engira Masilamani. The cinematography was handled by R. D. Rajasekhar and Sakthi Saravanan, with editing handled by Praveen K. L. The original score and soundtrack were composed by Yuvan Shankar Raja, with S. Thaman as the guest composer.

The film was released worldwide on 29 May 2015. A Telugu dubbed version, titled Rakshasudu, was released simultaneously in Andhra Pradesh and Telangana. It received mixed to positive reviews from critics and received praise for Surya's performance. The film was later remade in Bengali as Naqaab (2018), starring Shakib Khan, Nusrat Jahan and Sayantika Banerjee.