ERO may refer to:
- Edge recombination operator, an operator in genetic algorithms
- Electoral Registration Officer, a person is appointed by a local authority for the purpose of compiling and maintaining the electoral register
- Elementary row operations, in mathematics, certain operations that are performed on the rows of a matrix
- Extremely Red Objects, astronomical sources of radiation with extreme redshift
- Eugenics Record Office, a center for eugenics and human heredity research in America for the first half of the twentieth century.
- European Radiocommunications Office (now European Communications Office (ECO)), part of the European Conference of Postal and Telecommunications Administrations
- KonĨar-Arma ERO, a Croatian submachine gun similar to the Israeli-made Uzi submachine gun
- New Zealand Education Review Office