Bishop-designate Wickramasinghe succeeds Bishop Harold Anthony Perera, who was named Bishop of Kurunegala just over two years ago.
The newly appointed prelate was a moral theology professor at the National Seminary of Our Lady of Lanka.
The Diocese of Galle, near the southern tip of Sri Lanka, has less than 10,000 Catholics in a population of more than 2.5 million. They are served by 33 priests and about 100 religious. Sri Lanka is majority Buddhist (69.1%), with Muslims and Hindus each making up about 7% of the population, and Christians about 6%.
Raymond Wickramasinghe was born in 1962 and ordained in 1989.
