Angus Lorne Bonnycastle (November 3, 1873 – September 9, 1941) was a politician in Manitoba, Canada.
A member of the Bonnycastle family, his great-grandfather, Sir Richard Henry Bonnycastle, was a Lieutenant-Colonel in the Royal Engineers, and supervised building in Kingston, Ontario, Saint John, New Brunswick, and other Canadian cities.
Bonnycastle first ran for the Manitoba legislature in the 1903 provincial election, and lost to Liberal candidate W. J. Doig by 124 votes in Russell.
Despite being forty years old, Angus Bonnycastle volunteered to serve overseas with the Canadian Expeditionary Force during World War I.
At the end of the war, he was appointed a county court judge in Dauphin, Manitoba, a position held until his death there in 1941.