Unio may refer to:
Unio (bivalve), a genus of freshwater mussels Unio (sternwheeler), a steamboat that operated in Oregon, United States, in 1861, before being renamed Union UNI/O, an asynchronous serial bus UNIO Satu Mare, a Romanian machine-building company or Confederation of Unions for Professionals, a national trade union center in Norway
See also Unio Mystica, the union of the individual human soul with the Godhead Unio Trium Nationum, a 1438 pact formed by the three Estates of Transylvania Convergència i Unió, a political party in Catalonia United Indian Nations of Oklahoma, a Native American rights organization Unió Democràtica de Catalunya, a political party in Catalonia Unió Valenciana, a political party in Valencia Unió Mallorquina, a political party on Majorca