The Ontario Regiment (RCAC) is a Primary Reserve armoured reconnaissance regiment of the Canadian Army. The unit is based in downtown Oshawa, Ontario, and is named after Ontario County (1852–1973). Formed in 1866, and more commonly known as the 'Ontarios', 'black cats' or 'ONT R' (pronounced "ON-tar"), the regiment ranks among the oldest continuously serving Reserve (Militia) regiments in Canada and is one of the senior armoured regiments in the Royal Canadian Armoured Corps.