Mackenzie's Tigers refers to the group of militant supporters led by William Lyon Mackenzie during the Upper Canada Rebellion of 1837-1838. This group consisted mainly of discontented farmers, laborers, and reformists who sought to challenge the oligarchic rule of the Family Compact, aiming for political reform and greater representation in government. Their actions were characterized by a strong desire for democratic change and discontent with the existing political system, which they felt was unresponsive to the needs of the common people.