Bač (pronounced [ˈbatʃ]; German: Batsch,[2] Italian: Baccia)[citation needed] is a village northeast of Knežak in the Municipality of Ilirska Bistrica in the Inner Carniola region of Slovenia.

[3] The name Bač is related to the Slovene common noun beč '(stone- or wood-lined) hollow with a spring' (< *bъťъ), referring to a local geographical feature.

The Slavic word *bъťъ was borrowed from Latin buttis 'barrel' and is also the origin of the Slovene toponyms Beč and Buč.

[4] The ruins of Kalec Castle (also Na Kalcu; German: Steinberg or Stemberg)[2][5] stand northwest of Bač near the sources of the Pivka River.

[5] The local church in the settlement is dedicated to Saint Anne and belongs to the Parish of Knežak.