Mary Douglas Leakey, FBA (née Nicol, 6 February 1913 – 9 December 1996) was a British paleoanthropologist who discovered the first fossilised Proconsul skull, an extinct ape which is now believed to be ancestral to humans. She also discovered the robust Zinjanthropus skull at Olduvai Gorge in Tanzania, eastern Africa. For much of her career she worked with her husband, Louis Leakey, at Olduvai Gorge, where they uncovered fossils of ancient hominines and the earliest hominins, as well as the stone tools produced by the latter group. Mary Leakey developed a system for classifying the stone tools found at Olduvai. She discovered the Laetoli footprints, and at the Laetoli site she discovered hominin fossils that were more than 3.75 million years old.

During her career, Leakey discovered fifteen new species of animal. She also brought about the naming of a new genus.

In 1972, after the death of her husband, Leakey became director of excavations at Olduvai. She maintained the Leakey family tradition of palaeoanthropology by training her son, Richard, in the field.