He was born at Ancoats Hall on 22 February 1732 to Nicholas Mosley, Esq.
[1] The Mosleys were an old and distinguished Manchester family with medieval origins in Staffordshire.
His father died in 1734, and he was adopted by Sir Oswald Mosley, 2nd Baronet, of Rolleston (1705–1757),[2] his second cousin and godfather.
[4] On 24 March 1781, he was himself created a baronet in the Baronetage of Great Britain by George III.
[1] He was succeeded in the baronetcy by his grandson Sir Oswald Mosley, 2nd Baronet.