The Legislative Assembly of Ontario is the legislative chamber of the Canadian province of Ontario. Its elected members are known as Members of Provincial Parliament (MPPs). Bills passed by the Legislative Assembly are given royal assent by the lieutenant governor of Ontario to become law. Together, the Legislative Assembly and Lieutenant Governor make up the unicameral Legislature of Ontario or Parliament of Ontario. The assembly meets at the Ontario Legislative Building at Queen's Park in the provincial capital of Toronto.

The lieutenant governor of Ontario is the representative in Ontario of the monarch, who operates distinctly within the province but is also shared equally with the ten other jurisdictions of Canada, as well as the other Commonwealth realms and any subdivisions thereof, and resides predominantly in his oldest realm, the United Kingdom. The lieutenant governor of Ontario is appointed in the same manner as the other provincial viceroys in Canada and is similarly tasked with carrying out most of the monarch's constitutional and ceremonial duties. The current lieutenant governor of Ontario is Edith Dumont, sworn in on November 14, 2023.