John Thomas Fanning (1837–1911) was an American architect and hydraulic engineer.

His contribution to fluid mechanics and hydraulic engineering is in the Fanning friction factor which is used by engineers in the present age to calculate the frictional pressures losses in flows inside pipes.

[2] In 1861 he enlisted, and participated in the United States Civil War with the rank of colonel, until his discharge.

[2] In 1872 he moved to Manchester, New Hampshire, to design that city's new municipal water system.

He served in many professional capacities as a hydraulic engineer, including consulting for many railroads.