The Grenville Regiment (Lisgar Rifles) was an infantry regiment of the Non-Permanent Active Militia of the Canadian Militia (now the Canadian Army) based in Grenville County, Ontario.

In 1936, the regiment was converted to artillery and would later become part of the 50th Field Artillery Regiment (The Prince of Wales Rangers), RCA (currently on the Supplementary Order of Battle).

The volunteer companies were called out on active service during the Fenian Raids in 1866, serving along the St. Lawrence River frontier at Fort Wellington in Prescott.

[2] On the outbreak of the First World War, on August 6, 1914, the 56th Grenville Regiment was called out for active service as part of the St. Lawrence River Canal Patrol, guarding the locks and canals along the St. Lawrence River.

2 Company was headquartered in Iroquois, Dundas County from the mid-1890s until 1906, when it was transferred to Merrickville.