The Legislative Assembly of Ontario, is the legislature of the Canadian province of Ontario. It is located in the Legislative Buildings at Queen's Park in Toronto.

The British North America Act, 1867 section 69 stipulated "There shall be a Legislature for Ontario consisting of the Lieutenant-Governor and of One House, styled the Legislative Assembly of Ontario". The Legislative Assembly is unicameral, without an upper house (replacing the bicameral Legislative Assembly of Canada (lower house) and Legislative Council of Canada (upper house), with 103 seats representing ridings elected in a first-past-the-post system across the province.

The assembly is also known (informally) as the Ontario Provincial Parliament, the reason being that unlike most of the other Canadian provinces, members of this assembly refer to themselves as Members of the Provincial Parliament (MPPs) as opposed to Members of the Legislative Assembly (MLAs) and are the only province to do so in accordance with the resolution passed in the Assembly on April 7, 1938. However the Legislative Assembly Act (R.S.O. 1990) refers to "members of the Assembly".