William Thornhill is a fictional character from the novel "The Secret River," written by Kate Grenville. He is a poor Englishman who is transported to Australia as a convict in the early 19th century. The story follows his struggles to build a new life in a harsh and unfamiliar land. As Thornhill attempts to establish himself, he faces moral dilemmas and conflicts with the Indigenous Darug people. His journey reflects themes of colonization, survival, and the complexities of human relationships in a changing world. Thornhill's character embodies the challenges faced by many early settlers in Australia.