Ossillyator (az lotini oscillo — melappam), sistemai fizikai lappandaro guyand. Sistemam mekhanikie, ki dar nazdikii nuqtai muvozinat melappad, Ossillyatori klassiki nom giriftaast. Agar energiyai potensialii Ossillyator ba kvadrati tamoil az vaziyati muvozinat (in holat dar mavridhoi lappishhoi khurd joy dorad) mutanosib boshad, onro Ossillyatori mavzuni (garmoniki) menomand.
Mafhumi Ossillyatorro dar sistemahoi gayrimekhanikii lappandae, ki dar elektromagnetizm, akustika, nazariyai joziba va gayra ba amal meoyand, niz istifoda mebarand. Yake az namudhoi beshtar mamuli Ossillyatori elektri konturi lappandaest, ki doroi induktiviyat va gunjoish meboshad. Ossillyator dar nazariyai jismi sakht, nazariyai afkanishoti elektromagniti, nazariyai lappishi spektri molekulaho roli muhim mebozad.