This article provides the first comprehensive overview of the severity and impact of the Spanish flu in Belgium (1918–1919) and thereby makes a long overdue connection with the extensive international literature on pandemics in general and Spanish flu in particular. Leveraging ego documents (diaries), municipal-level excess mortality, and individual-level cause-of-death registers, we present new evidence on the chronology and spatial distribution of Spanish flu mortality in Belgium in 1918 and 1919 as well as social and demographic characteristics of the Spanish flu deaths in the city of Antwerp and discuss the government measures taken in the difficult context of the German occupation. In Belgium, our analysis shows that the chronology and geography of the Spanish flu cannot be seen in isolation from the vagaries of the First World War, in terms of soldiers and evacuees both acting as likely vectors of influenza transmission as well as inflating crude death rates at the municipal level. ... : Historical Social Research. Supplement No. 33 (2021) ...