William John McCart (August 7, 1872 – 1933) was an Ontario merchant and political figure.
He represented Stormont in the Legislative Assembly of Ontario from 1902 to 1904 and from 1908 to 1911 as a Liberal member.
He was born in Port Henry, New York, the son of John McCart.
McCart later moved to Toronto where he established a wholesale business dealing in fruit.
This article about an Ontario Liberal Party MPP is a stub.