James Hann (1799–1856) was an English mathematician, teacher and textbook writer.
Hann was born at Washington, County Durham, where his father was a colliery smith.
After working as a fireman at a pumping-station at Hebburn, he was for several years on one of the steamers used on the Tyne River for towing vessels.
An acquaintanceship with Wesley S. B. Woolhouse the mathematician led to Hann's obtaining a situation as calculator in the Nautical Almanac Office.
A few years later he was appointed writing-master, and then shortly mathematical master at King's College School, London; this post he held till his death.