Lieutenant-Colonel Sir Richard Henry Bonnycastle (30 September 1791 – 3 November 1847) was an officer of the British army active in Upper Canada. In his capacity as a military engineer, Bonnycastle oversaw the fortification of Fort Henry in modern Kingston, Ontario. Through his son, Henry William John Bonnycastle (1813–1888) would come a prominent Bonnycastle family of Canadian politicians and adventurers and the founder of Harlequin Enterprises, the world's largest publisher of romance novels.