What is the name of the largest primate that ever lived?

The largest primate known to have ever lived was Gigantopithecus.

Gigantopithecus was an extinct ape genus represented by the species Gigantopithecus blacki. It lived in southern China and nearby parts of Asia during the Pleistocene, roughly from two million to a few hundred thousand years ago. Researchers know it mainly from teeth and jaw fragments, not a complete skeleton.

Because the fossil evidence is limited, estimates of its height and weight remain uncertain. Older reconstructions portrayed it as a gigantic, gorilla-like ape, perhaps around three metres tall and weighing several hundred kilograms. Modern researchers stress that tooth size does not translate neatly into body size, but Gigantopithecus is still generally regarded as the largest primate recorded.

It was once proposed as a human relative, but current evidence places it closer to the orangutan branch of the ape family tree. The other choices are hominins or extinct human relatives, not the accepted answer for the largest known primate.