Megalonyx (Greek, "large claw") is an extinct genus of ground sloths of the family Megalonychidae endemic to North America from the Hemphillian of the Late Miocene through to the Rancholabrean of the Pleistocene, living from ~10.3 Mya—11,000 years ago, existing for approximately 10.289 million years. Type species, M. jeffersonii, measured about 3 m (9.8 ft) and weighted up to 1000 kilograms.