The Kantakuzina Katarina Branković Serbian Orthodox Secondary School (Serbo-Croatian: Srpska pravoslavna opća gimnazija Kantakuzina Katarina Branković, Српска православна општа гимназија Кантакузина Катарина Бранковић), abbreviated as SPOG, is a coeducational gymnasium (e.g. preparatory high school or grammar school) of the Metropolitanate of Zagreb and Ljubljana located in Zagreb, Croatia. It is the only non-seminary high school of the Serbian Orthodox Church in the former Yugoslavia.