William Henry Knight was an English portrait and genre painter.

Knight was born in Newbury, Berkshire where his father, John Knight, was a schoolmaster. He was to become a solicitor, but gave up his law studies after two of his paintings were accepted by the annual exhibition of the Society of British Artists. He moved to London in 1855, taking lodgings in Kennington Road, Lambeth, and supporting himself by drawing crayon portraits while studying in the British Museum and in the schools of the Royal Academy.

Following in the footsteps of William Mulready, he became a genre painter, his street scenes and interior scenes often showing children at play. His first contribution to the Royal Academy exhibition was Boys playing draughts in 1846; from that year until 1862 he was a constant exhibitor there. He also showed many pictures at the British Institution.