Henry Philibert Gaspard Darcy (Dijon, France, June 10, 1803-Paris, January 2, 1858), better known as Darcy, was a French hydraulic engineer. Graduated as a Bridge and Road Engineer, he is one of the modern pioneers in the supply of drinking water. He has played an important role in the development of his hometown.

Between 1834 and 1840, on behalf of the municipality of Dijon, he was directly responsible for the design and construction of the city's drinking water supply system, building a 12 km long underground adduction line designed by him. In 1847, piped water reached all the floors of all the buildings in Dijon, thus transforming this city into the second European city in terms of water supply, after Rome.

Darcy also contributes to the arrival of the train to Dijon.

In 1856, he published a treatise on the public fountains of Dijon, in which the formula that has since carried his name appears. From this formula a unit of measurement is deduced: a darcy, corresponding to the permeability of a body comparable to a continuous and isotropic medium, through which a homogeneous fluid with a viscosity equal to that of water at 20 °C moves at a speed of 1 cm/s under a pressure gradient of 1 atm/cm.

In 1857 he published another treatise related to his experimental investigations of the movement of water in pipes.