Transylvanian Saxon is the native German dialect of the Transylvanian Saxons, an ethnic German minority group from Transylvania in central Romania, and is also one of the three oldest ethnic German and German-speaking groups of the German diaspora in Central and Eastern Europe, along with the Baltic Germans and Zipser Germans. In addition, the Transylvanian Saxons are the eldest ethnic German group of all constituent others forming the broader community of the Germans of Romania.

The dialect is known by the endonym Siweberjesch Såksesch or just Såksesch; in German as Siebenbürgisch-Sächsisch, Siebenbürgisch-sächsischer Dialekt/Mundart, or Die siebenbürgisch-sächsische Sprache (obsolete German spelling: Siebenbürgisch Teutsch); in Transylvanian Landler dialect as Soksisch; in Hungarian as erdélyi szász nyelv; and in Romanian as limba săsească, săsește, or dialectul săsesc.

Linguistically, the Transylvanian Saxon dialect is very close to Luxembourgish (especially regarding its vocabulary). This is because many ancestors of the present-day Transylvanian Saxons stemmed from contemporary Luxembourg as early as the 12th century, especially in the area of contemporary Sibiu County (German: Kreis Hermannstadt), as part of the Ostsiedlung process. In their case, the Ostsiedlung colonisation process took place in southern, southeastern, and northeastern Transylvania for economic development, guarding the easternmost borders of the former Kingdom of Hungary as well as mining, especially in the area of Bistrița (German: Bistritz or Nösen, archaic form).

Consequently, the Transylvanian Saxon dialect has been spoken in the south, southeast, and northeast of Transylvania since the High Middle Ages onwards. In addition, the Transylvanian Saxon dialect is also similar to the Zipser German dialect spoken by the Zipsers in Spiš (German: Zips), northeastern Slovakia as well as Maramureș (i.e. Maramureș County) and Bukovina (i.e. Suceava County), northeastern Romania.

There are two main types or varieties of the dialect, more specifically northern Transylvanian Saxon (German: Nordsiebenbürgisch), spoken in Nösnerland (Romanian: Țara Năsăudului) including the dialect of Bistrița, and south Transylvanian Saxon (German: Südsiebenbürgisch), including, most notably, the dialect of Sibiu (German: Hermannstadt). In the process of its development, the Transylvanian Saxon dialect has been influenced by Romanian and Hungarian as well. Nowadays, given its relatively small number of native speakers worldwide, the dialect is severely endangered.

In terms of comparative linguistics, it pertains to the Moselle Franconian group of West Central German dialects. In this particular regard, it must be mentioned that it shares a consistent amount of lexical similarities with Luxembourgish.

The dialect was mainly spoken in Transylvania (contemporary central Romania), by native speakers of German, Flemish, and Walloon origins who were settled in the Kingdom of Hungary starting in the mid and mid-late 12th century (more specifically from approximately the 1140s/1150s to the 19th century). Over the passing of time, it had been consistently influenced by both Romanian and Hungarian given the centuries-long cohabitation of the Saxons with Romanians and Hungarians (mostly Szeklers) in the south, southeast, and northeast of Transylvania. The main areas where Transylvanian Saxon was spoken in Transylvania were southern and northern Transylvania.

In the contemporary era, the vast majority of the native speakers have emigrated in several waves, initially to Germany and Austria, but then subsequently to the US, Canada as well as other Western European countries, managing in the process to preserve (at least temporarily) their specific language there.