A. C. Sainuddin (12 May 1952 – 4 November 1999), mononymously known as Zainuddin, was an Indian actor, assistant director and comedian, who worked in Malayalam cinema.

Zainuddin started his career as a mimicry artist in Cochin Kalabhavan.^[2] He was expert in imitating actor Madhu,^[3] especially his mannerisms as Pareekkutty in Chemmeen. He first appeared in films like Chappa directed by P. A. Bakkar.^[3] He then went on to act in over 150 films in a span of 13 years from 1986 to 1999.

He was noted for his role as a siamese twin in the film Siamese Irattakal, which featured him as a conjoined twin to Maniyanpilla Raju. Zainuddin also excelled in his roles in Mimics Parade, Hitler, Kabooliwala, Lal Salaam, Kasargode Khaderbhai and Alanchery Thambrakkal. By the late of 1990s, he started to suffer from respiratory diseases. Zainuddin was a member of a stage programme organised by Association of Malayalam Movie Artists (AMMA) to raise funds for the families of deceased in the Kargil war of 1999, which happened to be his last stage programme.

He died of respiratory complications at a private hospital in Kochi on 4 November 1999. He was only 47 at the time of his death.^[3] His last credited role was in the film Ezhupunna Tharakan.

Zainuddin was married to Laila in 1982 who was working as a Hindi teacher in Government Vocational Higher Secondary School, and they have two sons Zinsil and Zinil.^[4]

Zinsil completed his M.B.A. He married Anfiya and he has tried his luck in a Malayalam movie, Puthumukhangal (2010).

Zinil completed his graduation in computer engineering.^[5][6] Zinil Zainudeen marked his acting debut in the 2014 Malayalam movie To Let Ambadi Talkies along with Arjun Ashokan.