Ariyadasa was born on 3 December 1922 in Unawatuna, Galle, Sri Lanka as the youngest of the family. His father V. K. Abraham Appuhamy was a farmer and mother Sisiliana Hamine was a housewife. He had three elder brothers and two elder sisters. Although named by his father, his older sister, Dayawathi, changed his name from Appuhamy to Ariyadasa. He had his primary education at Buddhist Mixed School in Unawatuna and received his secondary education at Mahinda College, Galle.
