Mary II became a central figure in the Protestant succession through her marriage to William of Orange in 1677. As the eldest daughter of James, duke of York, later James II, she possessed a hereditary claim that became politically decisive when opposition to her father's government culminated in William's invasion of England in 1688. Mary remained in the Netherlands during the expedition and arrived in England after James had fled.

In 1689 Parliament offered the crown jointly to William and Mary. Scotland also recognized them as sovereigns after a separate constitutional settlement. The English Bill of Rights restricted royal interference with Parliament and excluded Catholics from the throne. Mary accepted a joint monarchy in which William exercised the main direction of government, rather than insisting on sole rule through her stronger hereditary title.

She nevertheless governed actively during William's repeated absences on campaign. Working with ministers and a council, she handled appointments, military and naval matters, and fears of Jacobite conspiracy. In 1690 she managed affairs in England while William fought James in Ireland; later absences again required her to act as the resident sovereign. The arrangement made her responsibilities substantial even though political expectations and the terms of the regency limited her freedom of action.

Mary also shaped the court's buildings and collections. With William she developed Kensington Palace and supported rebuilding at Hampton Court, while her interest in ceramics and furnishings influenced royal interiors. Concern for injured sailors contributed to plans for the naval hospital at Greenwich, completed after her death. Her position created painful family divisions, including estrangement from her father and a serious quarrel with her sister Anne. She died of smallpox in December 1694, leaving William to reign alone. Her rule combined constitutional change with the practical work of wartime government.