Sultan Ismail Nasiruddin Shah ibni Almarhum Sultan Zainal Abidin III (born 1907 in Kuala Terengganu) was the fourth Yang di-Pertuan Agong (roughly equivalent to King) of Malaysia, and Sultan of Terengganu.

The third surviving son of Sultan Zainal Abidin III ibni Almarhum Sultan Ahmad II (reigned 1881-1918), his mother was a Thai commoner, Cik Maimunah binti Abdullah.

Educated at the Malay College Kuala Kangsar (MCKK), he served his two elder half-brothers as their aide de camp, before succeeding his deposed nephew in 1945 as Sultan of Terengganu. At the time he held the office of Tengku Paduka Raja.

A keen photographer, he served as Yang di-Pertuan Agong between September 21, 1965 and September 20, 1970. In 1969, during a period of racial strife in Malaysia, he declared a nationwide state-of-emergency, suspended parliament and installed the Majlis Gerakan Nasional (MAGERAN).

He died in September, 1979 and was buried at Masjid Abidin in Kuala Terengganu. His consort, Tengku Intan Zaharah, served as his Raja Permaisuri Agong.