Sinnathamby Thambithurai Ariaratnam is an engineer who was born in Chavakacheri, Sri Lanka on September 2, 1933. He graduated from the University of Ceylon with a B.Sc. in engineer in 1953, before obtaining a B.Sc. (1955) and M.Sc. (1956) at the University of London. In 1960 Ariaratnam completed a PhD in engineering at the University of Cambridge, followed by a Postdoctoral Fellowship at the University of Birmingham, before accepting a research association position (1961-1962) at the Brown University. He was named an Associate Professor of Civil Engineering at the University of Waterloo in 1962, becoming a Professor in 1962. Ariaratnam is recognized for his work in the field of random vibration and his contributions to research regarding stochastic modelling and nonlinear dynamics.