Samogitia, often known by its Lithuanian name Žemaitija (Samogitian: Žemaitėjė; see below for alternative and historical names) is one of the five cultural regions of Lithuania and formerly one of the two core administrative divisions of the Grand Duchy of Lithuania alongside Lithuania proper.

Žemaitija is located in northwestern Lithuania. Its capital city is Telšiai and the largest city is Šiauliai (located on the border between Samogitia and Aukštaitija). Throughout centuries, Samogitia developed a separate culture featuring diverse architecture, folk costumes, dances, songs, traditions, and a distinct Samogitian language.

Famous landmarks include Tauragė Castle, Plungė Manor and Hill of Crosses.

The region is primarily referred to by its Lithuanian name, Žemaitija, in both local and national contexts. The Latin-derived term Samogitia, once widely used in historical sources, largely fell out of common administrative and colloquial use in the 19th century. The name Žemaitija, derived from the Lithuanian words žemas ("low") and žemė ("land"), translates to "lowlands," reflecting the region’s geographical characteristics. While Samogitia persists in historical and academic discussions, it is considered an archaic exonym in modern contexts, with Žemaitija remaining the standard designation.

Ruthenian sources mentioned the region as жемотьская земля, Žemot'skaja zemlja; this gave rise to its Polish form, Żmudź, and probably to the Middle High German Sameiten, Samaythen. In Latin texts, the name is usually written as Samogitia, Samogetia, etc. The region is also known in English as Lower Lithuania or, in reference to its Yiddish names, זאַמעט Zamet or זאַמוט Zamut.

The largest city is Šiauliai (Šiaulē). Telšiai (Telšē) is the capital, although Medininkai (now Varniai; Varnē) was once the capital of the Duchy of Samogitia.

The major cities are:

Samogitia is bordered by Lithuania Minor in the south-west, Suvalkija in the south-east, Aukštaitija in the east, and Semigallia and Courland in the north.