Binary pulsars are excellent laboratories to test the building blocks of Einstein's theory of General
Relativity. One of these is Lorentz symmetry which states that physical phenomena appear the same for all inertially moving observers. We study the e ect of violations of Lorentz symmetry in the orbital evolution of binary pulsars and that it induces a much more rapid decay of the binary's orbital period due to the emission of dipolar radiation. The absence of such behavior in recent observations allows us to place the most stringent constraints on Lorentz violation in gravity, thus verifying one of the cornerstones of Einstein's theory much more accurately than any previous gravitational observation.