William Telemachus McManus (November 28, 1780 – January 18, 1835) was an American lawyer and politician from New York.
Then he studied law with John Bird, was admitted to the bar, and commenced practice in Troy, New York.
He married Catharina Coons, and they had four children, among them Jane (McManus) Cazneau (1807–1878).
The next year, he set out with his son Robert, his daughter Jane and a company of German settlers for Texas, which was then still part of Mexico.
The scheme failed when the German settlers refused to go beyond Matagorda, and McManus returned with his daughter to Brunswick, NY, in 1834, and died there soon after.