Marius Sebastian Ostrowski FRHistS FRSA (German: [ˈmaːʁɪʊs zɛˈbastɪan ɔsˈtʁɔvskiː]; born 12 December 1988) is a German-British political and social theorist, historian of ideas, policy researcher, and composer, based at the Blavatnik School of Government, University of Oxford. His research interests lie in the study of ideology and ideologies, focusing especially on how social contexts shape patterns of ordinary thinking and everyday behaviour. He also writes on the theory and history of social democracy, in particular its origins in interwar socialist reformist thought, and on progressive visions of European integration, including the prospects for a Europe-wide Universal Basic Income.