Sepp Straffner (31 January 1875 Bad Goisern – 29 October 1952) was an Austrian federal railway official and politician in the Greater German People's Party.
Straffner was active in Georg von Schönerer's German National Movement (Deutschnationale Bewegung).
In 1919 he was successful in the Constitutional Assembly elections, becoming a member of the Republic of German-Austria legislature, and from 1920 to 1923 and 1927 to 1934 a deputy in the National Council.
He was one of the three national presidents who on 4 March 1933 resigned his office during a debate on a railway strike, precipitating a constitutional crisis, the dissolution of parliament and the seizure of power by the Chancellor, Engelbert Dollfuss as dictator.
On 15 March 1933 Straffner tried to withdraw his resignation and reconvene the parliamentary session but Dollfuss had ordered the police to prevent this "undeclared meeting" ( „nicht angemeldete Versammlung“) or to disperse it if it occurred, even though many members of the Greater German and Social Democrat parties were already present in the chamber.