William Thornley was a painter of coastal scenes whose work is very similar to Hubert and Charles Thornley, who may have been members of the same family. He painted scenes of genre, architecture and landscapes as well. A number of the landscapes were of Belgium, Holland, Italy and Norway. However, it is for his seascapes that he is best remembered.
Thornley's works are beautifully detailed and show a masterful understanding of the moods of both weather and sea. They are often small in size and put together with fine detail and great artistic merit. Thornley's fishing scenes are spirited and similar in style to those of "Jock" Wilson, and are often painted in pairs. Thornley's works have always been popular when they appear on the art market.
He was believed to have first exhibited marines at the Royal Academy in 1859 from an address in Paddington, London and also at the British Institution from 1861 until it closed in 1867. He continued to exhibit at the Royal Academy until 1898.
Thornley also exhibited at the Paris Salon and the Salon of French Artists, receiving an honourable mention in 1881 and a third place medal in 1888.
William Thornley also went by the names Georges William and William A. Thornbery.