Regina, Saskatchewan, police and Royal Canadian Mounted Police ambush strikers participating in the On-to-Ottawa Trek.

Regina is the capital city of the Canadian province of Saskatchewan. The city is the second-largest in the province, and is a commercial centre for southern Saskatchewan. As of the 2021 census, Regina had a city population of 226,404, and a metropolitan area population of 249,217. It is governed by Regina City Council. The city is surrounded by the Rural Municipality of Sherwood No. 159.

The Royal Canadian Mounted Police is the national police service of Canada. The RCMP is an agency of the Government of Canada; it also provides police services under contract to 11 provinces and territories, over 150 municipalities, and 600 Indigenous communities. The RCMP is commonly known as the Mounties in English.

The On-to-Ottawa Trek was a mass protest movement in Canada in 1935 sparked by unrest among unemployed single men in federal relief camps principally in Western Canada. The trek started in Vancouver and, picking up reinforcements along the way, was conducted by riding traincars eastward. The trek was stopped in Regina where on July 1, 1935, police dispersed it with loss of life and mass arrests.