Born in Birmingham on 27 June 1855, he was educated at Sedgley Park College (nr Wolverhampton) till he left at the age of 14: first apprenticed to John Hardman & Co - artworkers primarily in stained glass design. Very soon, he was executing  most of the design for the firm and was responsible for windows in the north aisle of St Paul's and designs for St Mary's in Coventry.

Noticing William's great interest in painting, the company released him with regret (in 1880) and supported his further study by sending him to study painting in Antwerp under Verlat. From Antwerp he went on to Paris in 1881 where he remained absorbed until 1884. Returning to London, he shared a studio with his friends William Arthur BREAKSPEARE and Phil Whiting, and after some months of casting around for new painting grounds, with encouragement from Walter LANGLEY, Edwin HARRIS and Phil Whiting, he settled on Newlyn.

He is one of the painters in the 1884 Group Photograph of the 'brotherhood of the palette' at Newlyn. Here he painted Mackerel in the Bay, a large water colour, Ferdinand and Miranda (another watercolour, inspired by Shakespeare's The Tempest) and an oil portrait, The Burgomaster. He much enjoyed living and working in Newlyn, although the brightness of the sunlight directly affected his eyesight (causing increasing loss of sight in one eye), and having made his mark in the plein-air style, he discovered he preferred figure painting in his studio. 

In 1886 he returned permanently to live in Birmingham.  His mother, who had devotedly inspired him all his life, died in 1888, and he married in 1890, Bertha Mary Powell; eight children (two daughters who died young, and six sons) were born to them. He was one of the founding members of the Birmingham Art Circle, that group which laughingly claimed (perhaps rightly) that 'Birmingham had discovered Newlyn as a painterly place,' and their fortnightly meetings in each other's studios were a great source of friendship and inspiration. The Turner collation of letters, sketchbooks, coloured plates and essays, presents a life well spent in art. Wainwright died on 1 August, 1931, age 76 in Birmingham (GRO).