Raja Sir Muttaiya Annamalai Muthiah Chettiar (5 August 1905 – 12 May 1984) was an Indian banker, politician, philanthropist, socialite and cultural activist who served as Mayor of Madras city (1933) and Minister of Excise and Education (1936–37) in the provincial government of Madras Presidency.
He was holder of the hereditary title Kumar-rajah (1929–48) and later, Raja of Chettinad (1948–84).
Muthiah Chettiar's father Rajah Sir Annamalai Chettiar was also a famous educationist and along with him he founded the Annamalai University in the town of Chidambaram in Tamil Nadu.
He was also the third Nattukottai Chettiar to be knighted; the first two were his nephew and father.
The government of Tamil Nadu honoured him with the title Tamil Isai Kavalar.