Gravity waves are predicted by the Theory of Relativity, which claims that distortions in space travel at the speed of light away from a mass that moves.
Gravity waves have never been directly observed, and have even been the subject of a hoax:
|“||In 2010 researchers from the Laser Interferometer Gravitational-Wave Observatory detected the first direct evidence of gravitational waves — crucial proof of relativity. After thousands of hours of verification, they learned that the signal was a “blind injection,” an authorized prank by colleagues to check their work.||”|
-  Gravitational waves spotted from white-dwarf pair, BBC
-  Gravitational waves from black holes detected, BBC