Osa may refer to one of the following:Osa peninsula, a peninsula in Costa RicaOsa, Perm Krai, a town in Perm Krai, RussiaOsa, name of several rural localities in RussiaOsa class missile boat9K33 Osa (SA-8 Gecko), a Soviet surface-to-air missile launcherM79 Osa, an Eastern Bloc rocket launcherOsa , a genus of plants in the Rubiaceae familyOSA as an acronym can stand for:Obstructive Sleep ApneaOffice of Secret