Nikolai Alexandrovich Gezekhus (17.01.1845—1919) was a Russian physicist. He was born in St Petersburg. He was professor at Tomsk University, in 1888-89 its rector, and in 1889-1918 professor and rector of the St Petersburg Technological Institute.
His work was in the fields of acoustics, molecular physics, electricity, optics and radioactivity. He measured the speed of sound in air with an accuracy that was high for the time; he studied the sound conductivity of solids, electrification caused by friction, by splashing and by atomisation, and ball lightning; he studied the spheroidal state of liquids and elastic after-effect. He studied the influence of light on the conductivity of selenium and worked out a theory of the photosensitivity of selenium. He constructed a number of physical instruments, in particular an air calorimeter, a hygrometer, an ammeter and others. He studied the thermal action of radium.