Thornhill is a suburban community in the Regional Municipality of York in Ontario, Canada. It is split between the cities of Vaughan and Markham, lying along the north border of Toronto, centered on Yonge Street. Once a police village. According to the 2001 Census, Thornhill – Vaughan’s population was 56,361, and the population of Thornhill – Markham was 47,333. It is immediately south and south-west of Richmond Hill.