Sepp is a given name. When borne by Upper German-speaking people, it is often a nickname for Josef or other names related to Joseph.
Those bearing it include:
Joseph Sepp Blatter (born 1936), disgraced suspended president of FIFAJosef Bradl (1918-1982), Austria ski jumper and coachSepp Daxenberger (1962–2010), Bavarian politicianSepp De Roover (born 1984), Belgian footballerJosef Sepp Dietrich (1892–1966), World War II Oberst-Gruppenführer of the Waffen-SSSepp Ferstl (born 1954), German alpine skierJosef Sepp Herberger (1897–1977), German football player and managerJosef Hirtreiter (1909-1978), German SS sergeant and Holocaust war criminalSepp Holzer (born 1942), Austrian permaculturalist and consultant for natural agricultureJosef Hügi (1930-1995), Swiss footballerSepp Kerschbaumer (1913–1964), Italian terroristSepp Kusstatscher (born 1947), Italian politicianJosef Sepp Maier (born 1944), German goalkeeperJosef Oberhauser (1915–1979), German Nazi SS officerJosef Sepp Piontek (born 1940), German former football player and managerSepp Schönmetzler (born 1944), German figure skater, coach and journalistSepp Straffner (1875–1952), Austrian federal railway official and politicianJosef Uhlmann (1902–1968), German fencer, participated at the 1936 Summer OlympicsSepp Walcher (1954–1984), Austrian alpine skierSepp Weiler (1921–1997), German ski jumperSepp Weiß (born 1952), German former footballerJosef Wurmheller (1917–1944), German Luftwaffe aceJosef Sepp Zeilbauer (born 1952), Austrian retired decathlete