Moondram Pirai (transl. The third crescent) is a 1982 Indian Tamil-language romantic drama film written, directed and filmed by Balu Mahendra. The film stars Kamal Haasan and Sridevi, while Y. G. Mahendran, Silk Smitha and Poornam Viswanathan played ing roles. It revolves around a school teacher who rescues a woman with retrograde amnesia, from a brothel, and protects her in his house located in Ketti. The rest of the film shows how the woman recovers her memory with the teacher's help.

Moondram Pirai is the first film produced by G. Thyagarajan and G. Saravanan's Sathya Jyothi Films. It was predominantly shot in Ooty and Ketti, with further shooting also taking place in Bangalore. The music for the film was composed by Ilaiyaraaja, with lyrics written by Kannadasan, Vairamuthu and Gangai Amaran. It also featured the last song written by Kannadasan to be recorded before his death in 1981.

Moondram Pirai was released on 19 February 1982 and received critical acclaim. It was a box office success and had a theatrical run of over a year. The film won two National Film Awards: Best Actor for Kamal Haasan, and Best Cinematography for Balu Mahendra. It also won the Best Director – Tamil award for Balu Mahendra at the Filmfare Awards South, and five Tamil Nadu State Film Awards, including Best Film (third prize), Best Actor (Kamal) and Best Actress (Sridevi). Mahendra remade the film in Hindi as Sa (1983), with Kamal Haasan, Sridevi and Smitha reprising their roles.