The Athabasca oil sands, also known as the Athabasca tar sands, are large deposits of bitumen, a heavy and viscous form of petroleum, located in northeastern Alberta, Canada. These reserves are one of the largest sources of unconventional oil in the world, making Canada a significant player in the global energy market.

Bitumen is an immensely viscous constituent of petroleum. Depending on its exact composition it can be a sticky, black liquid or an apparently solid mass that behaves as a liquid over very large time scales. In American English, the material is commonly referred to as asphalt. Whether found in natural deposits or refined from petroleum, the substance is classed as a pitch. Prior to the 20th century the term asphaltum was in general use. The word derives from the ancient Greek ἄσφαλτος ásphaltos, which referred to natural bitumen or pitch. The largest natural deposit of bitumen in the world is the Pitch Lake of southwest Trinidad, which is estimated to contain 10 million tons.