By the onset of World War I, hundreds of Ottoman immigrants, including a significant proportion of Jews, were living and trading in Britain. During wartime and through much of the interwar period, these multi-ethnic Ottomans were automatically classified as enemy aliens, subject at times to internment and deportation, stripped of their freedom of movement, and uniformly barred from citizenship. Drawing on nearly sixty recently declassified naturalization applications of Ottoman Jews, this article discusses the prosopography of Middle Eastern newcomers, nativism and xenophobia, and the role of the state in shaping national and ethnic identities, focusing on the British government’s invention of an ‘Ottoman (Spanish Jew)’ designation that legally Hispanicised Ottoman Jewish applicants, allowing them to be considered for citizenship.