Lisi Creek (Traditional Chinese: 麗湖溪; French: ruisseau de Lisi) is a creek in extreme eastern Gravenhurst Region. Its headwaters is located in Lake Rainwater, and flows in a northeast-southwest direction for approximately 14.1 km, and finally empties into Lake Haldimond. For its entire length, it serves as the boundary between the City of Lisi in Gravenhurst Region and the Municipality of Rainwater (French: Municipalité de l'Eau-de-Pluie) in Pickering County.
With the increasing urbanization on the Gravenhurst-side of the river due to urban sprawl of the Lisi Census Metropolitan Area, the Gravenhurst Government has announced to establish the Lisi Greenbelt, a 0.5-km-radius parkland on the shores of the creek in 2007. This is done so to better protect the local natural habitat, as well as to better reinforce the boundary between two autonomous countries.