The **Lorentz transformation**, named after its discoverer, a Dutch physicist and mathematician Hendrik Antoon Lorentz (1853-1928), forms the basis for the special theory of relativity, that has been introduced to remove contradictions between the theories of electromagnetism and classical mechanics.

Under these transformations, the speed of light is the same in all reference frames, as postulated by special relativity. Although the equations are associated with special relativity, they were developed before special relativity and were proposed by Lorentz in 1904 as a means of explaining the Michelson-Morley experiment through contraction of lengths. This is in contrast to the more intuitive Galilean transformation, which is sufficient at non-relativistic speeds.

It can be used (for example) to calculate how a particle trajectory looks like if viewed from an inertial reference frame that is moving with constant velocity (with respect to the initial reference frame). It replaces the earlier Galilean transformation. The velocity of light, *c*, enters as a parameter in the Lorentz transformation. If *c* is taken to be infinite, the Galilean transformation is recovered, such that it may be indentified as a limiting case.

The Lorentz transformation is a group transformation that is used to transform the space and time coordinates (or in general any four-vector) of one inertial reference frame, , into those of another one, , with traveling at a relative speed of to . If an event has space-time coordinates of in and in , then these are related according to the Lorentz transformation in the following way:

These equations only work if is pointed along the x-axis of . In cases where does not point along the x-axis of , it is generally easier to perform a rotation so that does point along the x-axis of than to bother with the general case of the Lorentz transformation. Another limiting factor of the above transformation is that the "position" of the origins must coincide at 0. What this means is that in frame must be the same as in . This, of course, simply means we are dealing with Lorentz transformations, not Poincaré ones.

More generally, If Λ is any 4x4 matrix such that Λ^{T}*g*Λ=*g*, where T stands for transpose and

Under the Erlanger program, Minkowski space can be viewed as the geometry defined by the Poincaré group, which combines Lorentz transformations with translations.

Lorentz discovered in 1900 that the transformation preserved Maxwell's equations. Lorentz believed the luminiferous aether hypothesis; it was Albert Einstein who developed the theory of relativity to provide a proper foundation for its application.