The Municipality of Postojna (pronounced [pɔˈstoːi̯na] ⓘ; Slovene: Občina Postojna) is a municipality in the traditional region of Inner Carniola in southwestern Slovenia.

The seat of the municipality is the town of Postojna.

[2] The municipality was established in its current form on 3 October 1994, when the former larger Municipality of Postojna was subdivided into the municipalities of Pivka and Postojna.

One of Slovenia's major tourist attractions, Postojna Cave, is located in the municipality.

A second popular tourist attraction, located approximately 9 kilometers (5.6 mi) from Postojna, is Predjama Castle, a 16th-century castle built in the mouth of another karst cave.