Homi Nusserwanji Sethna (24 August 1923 – 5 September 2010) was an Indian nuclear scientist and a chemical engineer, gaining international fame as the Chairman of the Atomic Energy Commission (India) during the time when the first nuclear test, codename Smiling Buddha in Pokhran Test Range in 1974 was conducted.

Earlier in his career, he had full technical responsibility for setting up of the Thorium extraction plant at Alwaye, Kerala India, for separation of rare earth from monazite sands.

Homi Sethna was born to a Parsi family on 24 August 1923 in Bombay (now Mumbai).

His first major challenging assignment was the setting up of the Plutonium Plant at Trombay in 1959.

He was the guiding force behind the first peaceful nuclear explosion, Project Smiling Buddha in India on 18 May 1974,[5] and in 1975, Homi Sethna, then chairman of the Atomic Energy Commission, Raja Ramanna and Basanti Dulal Nagchaudhuri (head of the DRDO) received the Padma Vibhushan.