Robert Nelles (October 6, 1761 – July 27, 1842) was a businessman and political figure in Upper Canada.
He was born in Tryon County, New York in 1761. His father served in the Indian Department. Robert was made a lieutenant in the department in 1780 and served during the American Revolution, leading raids into the interior of New York state. After the war, father and son settled in the Grand River valley and received several large land grants in the Niagara District. Nelles built mills and a store on the current site of the town of Grimsby. In 1797, he was appointed Indian agent in the region for a brief time. In 1800, he was elected to the Legislative Assembly of Upper Canada in West York, 1st Lincoln & Haldimand and served until 1808. He joined the local militia during the War of 1812, eventually becoming lieutenant-colonel. In 1814, he replaced Joseph Willcocks in the legislative assembly in a by-election for 1st Lincoln and Haldimand, serving until 1820.
He died in Grimsby in 1842.