The Gray's monitor (Varanus olivaceus) is a large (180 cm, >9 kg) monitor lizard known only from lowland dipterocarp forest in southern Luzon, Catanduanes, and Polillo Island, all islands in the Philippines. It is also known as Gray's monitor lizard, butaan, and ornate monitor. It belongs to the subgenus Philippinosaurus. It is largely arboreal and extremely shy.