Lieutenant-Colonel Henry James Grasett CMG (June 18, 1847 – September 30, 1930) was a Canadian army and militia officer who served as a Toronto police chief.
He fought on the Niagara Peninsula during the Fenian raid of 1866 with the 2nd Battalion, Volunteer Militia Rifles of Toronto, In 1867, he joined the British Army serving as an ensign with 100th (Prince of Wales's Royal Canadian) Regiment of Foot in Canada and England and rose to the rank of lieutenant by the time he retired to Toronto in 1875, where he became a partner in a firm of shipping and commission merchants.
In 1885, he was given the rank of lieutenant colonel in the militia and put in command of the 10th Battalion Royal Grenadiers which fought in several battles during the North-West Rebellion of 1885.
He also oversaw innovations such as the institution of an electric call box and signal system, patrol wagons, bicycles, motorcycles and ultimately police cars and also reorganized the morality squad and department of detectives.
At the provincial commission that was created to investigate the unrest, Grasett expressed his opposition to one of the union's key demands, promotion by seniority.