[1][2][3][4] It was originally formed as the Toronto Mounted Rifles at Toronto, Ontario, on April 1, 1901, by combining J and K Squadrons of the Canadian Mounted Rifles with three newly raised companies.

[6][7] This was a reference to the First Nation that inhabited the area before the Europeans, the Mississaugas.

The 9th Mississauga Horse contributed many volunteers to the Canadian Expeditionary Force during World War I, in particular to the 75th Battalion and the 170th (Mississauga Horse) Battalion, CEF.

On 15 December 1936, as part of the 1936 Canadian Militia Reorganization, the regiment was amalgamated with The Governor General's Body Guard to form The Governor General's Horse Guards, an armoured militia (i.e., part-time reservist) regiment, which still exists today as part of 32 Canadian Brigade Group in Toronto.

[10][11][12][13] In 1929 the regiment was awarded battle honours for the Great War.