Dalton James Patrick McGuinty Jr. is a former Canadian politician who served as the 24th premier of Ontario from 2003 to 2013. He was the first Liberal leader to win two majority governments since Mitchell Hepburn nearly 70 years earlier. In 2011, he became the first Liberal premier to secure a third consecutive term since Oliver Mowat after his party was re-elected in that year's provincial election.

The premier of Ontario is the head of government of Ontario. Under the Westminster system, the premier governs with the confidence of a majority the elected Legislative Assembly; as such, the premier typically sits as a member of Provincial Parliament (MPP) and leads the largest party or a coalition of parties. As first minister, the premier selects ministers to form the Executive Council, and serves as its chair. Constitutionally, the Crown exercises executive power on the advice of the Executive Council, which is collectively responsible to the legislature.