"Egg Stealer" is a term used in The Land Before Time for dinosaur species that primarily eat eggs, particularly Struthiomimus, a creature which is depicted as an egg thief in the first few films in the series. The only named egg stealers to appear are Ozzy and Strut. The first egg stealer, a Struthiomimus, to appear is in the The Land Before Time, which (unsuccessfully) attempts to steal the egg which Littlefoot hatches from shortly afterwards. They also appear in the sequence depicting the Great Earthshake, attempting to flee the devastation wrought by calamitous event.
In The Land Before Time IV: Journey Through the Mists, an egg stealer flock jumps into a river after the Prehistoric Pals first reach the Land of Mists. Egg Stealers have not appeared in the series since the fourth film.