Ostenk (pronounced [ɔˈsteːŋk]; sometimes Ostenik[2]) is a settlement in the Municipality of Trbovlje in central Slovenia.

[2] The name of the settlement was changed from Sveti Marko (literally, 'Saint Mark') to Ostenk in 1955.

The name was changed on the basis of the 1948 Law on Names of Settlements and Designations of Squares, Streets, and Buildings as part of efforts by Slovenia's postwar communist government to remove religious elements from toponyms.

The name Jelšje now refers to a hamlet of Ostenk northwest of the main settlement.

[2] The local church is dedicated to Saint Mark and belongs to the Parish of Trbovlje.