The Transylvanian Saxons are a Germanic people who settled in Transylvania in various waves from the 12th-century Ostsiedlung to the mid-19th century. They were mostly Luxembourgish, from the Low Countries as well as Alsace in modern day France, but also from other parts of present-day Germany.

The first ancestors of the Transylvanian 'Saxons' originally stemmed from Flanders, Hainaut, Brabant, Liège, Zeeland, Moselle, Lorraine, and Luxembourg, then situated in the north-western territories of the Holy Roman Empire around the 1140s and 1150s.

Alongside the Baltic Germans from Estonia and Latvia and the Zipser Germans (also sometimes known or referred to as Zipser Saxons) from Zips, northeastern Slovakia, as well as Maramureș and Bucovina, the Transylvanian Saxons are one of the three eldest German-speaking and ethnic German groups of the German diaspora in Central-Eastern Europe, having continuously been living there since the High Middle Ages onwards. The Transylvanian Saxons are part of the broader group of Romanian Germans as well, being the eldest of all the constituent sub-groups of this ethnic community.

Their native dialect, Transylvanian Saxon, is close to Luxembourgish. Nowadays, organisations representing the Transylvanian Saxons exist in Romania, Germany, Austria, Canada, and the United States (in the latter case most notably 'Alliance of Transylvanian Saxons'). Other smaller communities of Transylvanian Saxons can be found in South Africa and Australia as well as South America (for example in Argentina).

Although most Transylvanian Saxons did not descend from the medieval Saxons, the latter name was historically often used pars pro toto to describe any Germanic peoples. In the vicinity of Transylvania —Romania, Hungary, and Moldova— the Transylvanian Saxons are usually called simply "Saxons", with "Transylvanian" taken for granted. Names for (Transylvanian) Saxons in local languages include:

The legal foundation of their settlement in southern, southeastern, and northeastern Transylvania was officially stipulated within the Diploma Andreanum (German: Der Goldene Freibrief der Siebenbürger Sachsen, The Golden Charter of the Transylvanian Saxons, Romanian: Bula de aur a sașilor transilvăneni) issued by King Andrew II of Hungary, which allocated them a territory to be held under their own local autonomy, known as Königsboden in German or Fundus Regius in Latin lit. "royal land" (Romanian: Pământul crăiesc or Pământul regal).

The ancestors of the modern Transylvanian Saxons originally came from the contemporary Low Countries (more specifically the regions of Flanders, Hainaut, Brabant, Liège, or Zeeland) as well as the Moselle and Lorraine river valleys, and Luxembourg as well, which around the 1140s were part of the north-western territories of the Holy Roman Empire. Further or subsequent waves of German colonists in Transylvania also stemmed from more southern regions of present-day Germany such as Thuringia or even Bavaria (the latter particularly valid for the Saxons in northeastern Transylvania). The initial waves of Transylvanian Saxons were referred to as hospites flandrenses et teutonici or primi hospites regni in Latin, literally "the Flemish and Teutonic guests" or "the first guests of the kingdom" (i.e. of the former Kingdom of Hungary).

For centuries, the main tasks of the Transylvanian Saxons during the High Middle Ages were to protect the easternmost frontiers of the former Kingdom of Hungary against certain invading migratory Asiatic peoples, to bring more agriculture to the region, to instil Central European culture, enhance trade, and boost urbanisation and overall economic development. In the process of fortifying the borders of the Kingdom of Hungary to the east, they were early on helped by the Teutonic Knights. Later on, they had to further strengthen their hometowns and rural settlements against the expanding Ottoman Empire, which posed a major threat from the south. The rural settlements defended themselves by fortifying their churches into small fortresses, known as either 'Wehrkirchen [de]' (fortified churches) or 'Kirchenburgen [de]' (church fortress) in standard German.