The Library of Skulls is a highly knowledgeable sentient "library" used by the Sleestaks in the 1974 TV series Land of the Lost and its 2009 movie adaptation.
The Library of Skulls is located in the Lost City. It is a foggy cavern containing glowing Altrusian skulls and urns on pedestals and ledges. The urns emit a "sacred smoke" that induces a form of telepathy that allows the user to communicate with the Skulls, however a lengthy exposure to the smoke causes hallucinations.
The Skulls are databases that can tell information through voices. They are even able to predict or prophesize the future. Each Skull has a different areas of expertise or specialization ("Skull of History", "Skull of Wisdom", etc.). Despite being sentient, they don't have any specific goals.
The Sleestaks always consult the Library of Skulls for advice on important matters, especially the Sleestak Leader and Enik. However, under some circumstances, others may also ask questions. The Sleestaks have an immense respect for the Skulls, and never question them.