In zoological nomenclature, a name which has not been used in the scientific community for more than fifty years after its original proposal, and which has been replaced by a more recent name in common use.

A nomen oblitum comes from Latin, "forgotten name" and it is a technical term, used in zoology.

In its present meaning, it came into existence with the fourth, 1999, edition of the International Code of Zoological Nomenclature.

After January 1, 2000, a scientific name could be formally declared to be a nomen oblitum if it had not been used in the scientific community since 1899, and when it was either a senior synonym or a homonym; that is, spelled the same as another name, which is in common use.