SF Ammonia is a steam-powered railway ferry on Lake Tinn in Telemark, Norway.

This system was used by Norsk Hydro to transport chemicals from Rjukan to the port in Skien.

[1] Ammonia is capable of carrying 17 railway cars, totalling 630 tonnes, on 120 metres of track – double-track standard gauge, in addition to 150 passengers.

She has two steam engines each of 300 kW (400 hp), and can achieve a speed of 12 knots (22 km/h).

After the sinking of Hydro in 1944, Ammonia had to do the main hauling across the lake, and by September 1944 she was performing eight round trips each day.