Dr Josef "Sepp" Janko (9 November 1905, Ernsthausen (Hungarian: Ernesztháza, Ernőháza, Serbian: (now) Банатски Деспотовац, Banatski Despotovac), the Bánát (Банат, Bánság) (present-day Central Banat, Vojvodina), Kingdom of Serbia, Austria-Hungary — 25 September 2001, Buenos Aires, Argentina) was Volksgruppenführer ("Group Leader") of the Danube Swabian German Cultural Association (Schwäbisch-Deutschen Kulturbundes) in Yugoslavia in 1939, and later was appointed SS Obersturmführer during World War II.
Janko was born on 9 November 1905 in Ernsthausen (Serbian: Ernestovac) to a Roman Catholic farming family of Swabian descent. He studied law in Graz.
Janko was a moderate fascist in politics and on 6 June 1939 he was elected the president of the Swabian-German Cultural Association in Yugoslavia at the suggestion of the Reich agency Volksdeutsche Mittelstelle (VoMi). On 12 December 1940, he was awarded the Yugoslav Kronen-Orden Class III by Prime Minister Dragiša Cvetković. After the invasion of the Wehrmacht early in 1941, the Cultural Association was disbanded and VoMi organised the Deutsche Volksgruppe in Serbien und Banat (DVSB) under Janko's leadership. Janko was simultaneously appointed an SS Obersturmführer in the Nazi-occupied Banat region of Serbia.