Sir Chetput Pattabhiraman Ramaswami Iyer (12 November 1879 – 26 September 1966), popularly known as Sir C. P., was an Indian lawyer, administrator and politician who served as the Advocate-General of Madras Presidency from 1920 to 1923, Law member of the Executive council of the Governor of Madras from 1923 to 1928, Law member of the Executive Council of the Viceroy of India from 1931 to 1936 and the Diwan of Travancore from 1936 to 1947. Ramaswami Iyer was born in 1879 in Madras city and studied at Wesley College High School and Presidency College, Madras before qualifying as a lawyer from the Madras Law College. He practised as a lawyer in Madras and succeeded S. Srinivasa Iyengar as the Advocate-General of the Madras Presidency. He subsequently served as the Law member of the Governor of Madras and of the Viceroy of India before being appointed Diwan of Travancore in 1936.

Ramaswami Iyer served as Diwan from 1936 to 1947; during his tenure, many social and administrative reforms were made. However, at the same time, he is also remembered for the ruthless suppression of the communist-organised Punnapra-Vayalar revolt, and his controversial stand in favour of an independent Travancore. He resigned in 1947 following a failed assassination attempt. He served as a leader of the Indian National Congress in his early days. He was made a Knight Commander of the Indian Empire in 1926 and a Knight Commander of the Star of India in 1941. He returned these titles when India attained independence in 1947. He was also a member of the 1926 and 1927 delegations to the League of Nations. In his later life he served in numerous international organisations and on the board of several Indian universities. Ramaswami Iyer died in 1966 at the age of 86 while on a visit to the United Kingdom.