Neanderthal 1 is the name of the first fossil found that was clearly identified as a Neanderthal (Homo neanderthalensis). Sometimes this fossil is also called Feldhofer 1, but that name is less common.
It is not the first fossil found of a Neanderthal, but before this find, the importance of the fossils was unclear. The fossil is part of a skull, with a fragment of the left temporal bone, part of the right scapula (shoulder blade), the right clavicle, both humeri (bones in the upper arm), one radius (a bone in the forearm), both ulnae (another bone in the forearm), five ribs, an almost complete half pelvis, and both femurs.