Leader of the Official Opposition (Ontario)

The leader of the Official Opposition (French: chef de l'Opposition officielle) is the leader of the largest political party in the Legislative Assembly of Ontario that is not in government and is typically the second-largest party. The position is formally titled the leader of His Majesty's Loyal Opposition (French: chef de la loyale opposition de Sa Majesté); under the Westminster system, while the parliamentary opposition opposes the incumbent government, it remains loyal to the Crown and thus to Canada.

Marit Stiles has served as the leader of the Official Opposition since February 4, 2023. She leads the New Democratic Party (NDP), which has held the second largest number of seats in the Legislative Assembly since the 2018 provincial election.