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Henry Girdlestone Acres (1880-1945) was a hydroelectric engineer from St. Catharines, Canada.^[1]

Acres was born in Paris, Ontario, and was educated at the University of Toronto.^[2] In 1908, he married Augusta Louise Helliwell Acres. They had a daughter, Constance, who died in 1939.^[2]

Acres contributed to the design and oversight of the Chippawa-Queenston Project for the Ontario Hydro-Electric Power Commission and the Shipshaw development in Arvida, Quebec.^[2] The latter was inaugurated in 1942 as the world's largest localized power development.^[2]

In 1905, Acres was involved in the introduction of a 10,000-horsepower turbine.^[2] In 1907, he oversaw the establishment of the first 110,000-volt transmission line.^[2] Throughout his career, he worked with multiple Canadian organizations, including the Hydro-Electric Power Commission of Ontario and Vickers.^[2]