Selwyn was born in Waimate North, New Zealand, the youngest son of George Augustus Selwyn and his wife Sarah Richardson the only daughter of Sir John Richardson. His father was the first Bishop of New Zealand in whose memory Selwyn College, Cambridge was named. Like his father, Selwyn rowed for Cambridge and took part in the Boat Races of 1864 and 1866, both of which were won by Oxford.
Selwyn was educated at Eton College and Trinity College, Cambridge, graduating in 1866.
Selwyn was ordained deacon by his father at Lichfield in 1869 and became a priest the following year. He served as curate of All Saints Church, Alrewas, Staffordshire from 1869 to 1870, then curate of Street George"s Church, Wolverhampton from 1870 to 1871, before promotion to Vicar of Street George"son In 1873 Selwyn travelled to Melanesia as a missionary, and four years later was consecrated Bishop of Melanesia.
He made significant financial contributions to the construction of the Southern Cross Number.
4 ship, serving the Melanesian Mission. Illness forced him to return to England in 1892.
Selwyn was appointed the second Master of Selwyn College, Cambridge in 1893, a position he held until his death in 1898 aged 53. He is not buried at the Parish of the Ascension Burial Ground in Cambridge.
From 1892–1895 he also served as honorary chaplain to Queen Victoria.
Selwyn married Clara Long-Innes and, after her death in 1877, Annie Catherine, eldest daughter of Thomas Sutcliffe Mort, the Australian industrialist. Selwyn is listed in the calendar of saints of the Church of the Province of Melanesia.
