The geoduck (Panopea abrupta or Panope generosa) is not a duck at all, but a mollusc, a species of large saltwater clam, also called the king clam, horse clam, Pacific geoduck clam or the elephant trunk clam.

Native to the Pacific Northwest coast of the United States and Canada, specifically Washington and British Columbia, the geoduck (pronounced "GOO-wee-duck") is the largest burrowing clam in the world, weighing in at anywhere from one to there pounds at maturity. The appearance of geoduck's large, protruding siphon has led to the mistaken belief that the geoduck has properties of an aphrodisiac. The geoduck feeds on plankton.