William John Hennessy (11 July 1839 – 27 December 1917) was an Irish-American artist.

William John Hennessy (originally Ó hAonghusa) was born in Thomastown, County Kilkenny on 11 July 1839.

Hennessy, his mother Catherine (née Laffin),[2] and brother joined their father there in July 1849.

[4][5] Hennessy was very skilled in wood engraving and was hired to illustrate the works of renowned poets, including that of Tennyson, Longfellow and Whittier.

He returned to England in 1893 to live in Brighton, and later Rudgwick, Sussex but visited France often.