Woldemar Voigt (September 2, 1850 - December 13, 1919) was a German physicist.

He was born in Leipzig, and died in Göttingen. He was a student of Franz Ernst Neumann. He worked on crystal physics, thermodynamics and electro-optics. His main work was the Lehrbuch der Kristallphysik (Textbook on crystal physics), first published in 1910.

It was Voigt who was the first to formulate the Lorentz transformation in his 1887 article Über das Doppler'sche Princip (On the Doppler Effect), where he stated the universal speed of light. He was also the first to demonstrate that Maxwell's equations are invariant under the Lorentz transformation.

The word tensor in its current meaning was introduced by Voigt in 1899.