Clifford Timothy O’Riordan was born in Mascot, Sydney, to Catholic parents Michael and Julia O’Riordan on 12 May 1909. He was educated at St. Ignatius College Riverview, and while he was a student there participated in rowing and athletics. In 1936, O’Riordan received his degree and became a barrister in Sydney. He practiced law from his chambers on Philip Street, and specialised in divorce law.

O’Riordan enlisted in the RAAF on 6 January 1941, and served with No. 460 Squadron and No. 103 Squadron. He was involved in many significant bombing raids over Germany and Italy as a gunner in his crew. While serving, O’Riordan also used his skills in law by being the defendant for those in his squadron who were involved in Court Martials. Flying Officer O'Riordan's Lancaster ED 525 bomber was shot down over Hamburg, Germany, on 30 July 1943 (night of 29-30 July), killing all seven crew members. He is buried in Becklingen War Cemetery, Luneburg, Germany.