HCO may refer to:
In arts and entertainment Hobart Chamber Orchestra Hollywood Chamber Orchestra
In science and technology Aldehyde (HCO-) Harvard College Observatory Hearing carry over, a type of telecommunications relay service Heliocentric orbit, an orbit around the Sun Holocene climatic optimum
Businesses and organizations Handball Club Odense, a Danish handball club Hans Christian Ørsted Institute (HCØ) Hollister Co., an American lifestyle brand National Socialist Society (Russian: ) Hanwell Community Observatory, a public outreach astronomy organisation; see Hanwell, Oxfordshire Hubbard Communications Office, an organization in the Church of Scientology