SF Hydro was a Norwegian steam powered railway ferry that operated in the first half of the 20th century on the lake Tinnsjø in Telemark. It connected with the two railways Rjukanbanen and Tinnosbanen, at Mæl and Tinnoset, operating between 1914 and 1944. The combined track and ferry service was primarily used to transport raw materials and fertilizer from Norsk Hydro's factory at Rjukan to the port in Skien.