The Princely House of Thurn and Taxis (German: Fürstenhaus von Thurn und Taxis, [ˈtuːɐ̯n ʔʊnt ˈtaksɪs], Italian: della Torre e Tasso, French: de la Tour et Tassis) is a German noble family that originated in Lombardy (Italy). It was a key player in the postal services in Europe; its operations began around 1290 in the Bergamo region, and from the 16th to the 19th century, it maintained significant, Europe-wide networks with headquarters in Brussels and Frankfurt.

From the 14th century onwards, it operated a relay courier service between numerous European capitals; from this, a private postal enterprise evolved starting in 1490, followed by the Kaiserliche Reichspost (Imperial Post) which was operated by the family from around 1600 to 1806, followed by the Thurn-und-Taxis Post between 1806 and 1867.

By investing the proceeds from its postal business − and later the compensations received for its postal rights – into numerous landed estates in Southern Germany during the 18th and 19th centuries, the family became, and remains to this day, Germany's largest private forest owner. It also operated a brewery and a private bank.

The family, raised to the rank of baron in 1608 and count in 1624, added Thurn to its original surname, Taxis, starting in 1650. In 1681, the Brussels branch was raised to the rank of prince in the Spanish Netherlands, and in 1695 to the rank of prince of the Holy Roman Empire. From 1615, the heads of the family held the title of Hereditary Postmaster General of the Holy Roman Empire. Admission to the Council of Princes of the Imperial Diet took place in 1704. The Imperial Diet was based in Regensburg. When the head of the family, Prince Alexander, assumed the office of the Emperor's representative (Principal Commissioner) at the Perpetual Diet – and thus the presidency of that parliament – in 1741, he relocated from Frankfurt to Regensburg. His descendants held this office until the end of the Empire in 1806. In 1812, the family acquired the buildings and lands of the significant former Imperial Saint Emmeram's Abbey there; since then, the site has remained their place of residence and business headquarters under the name St Emmeram's Palace. The current head of the House is Albert, 12th Prince of Thurn and Taxis.

They are one of the mediatised Houses for their former sovereign Imperial counties, acquired in the 18th century, which were consolidated into a principality in 1803 (Principality of Buchau), consisting of the lands of five secularized imperial abbeys, though it lost its political independence as early as 1806 when it was mediatised to the Kingdom of Württemberg, and in smaller parts to the Kingdom of Bavaria and the principality of Hohenzollern-Sigmaringen.

The Tasso family (from the Italian word for "badger", the family's heraldic animal) was a Lombard family in the area of Bergamo. The earliest records place them in Almenno in the Val Brembana around 1200, before they fled to the more distant village of Cornello to escape feuding between Bergamo's Colleoni (Guelf) and Suardi (Ghibelline) families. Around 1290, after Milan had conquered Bergamo, Omodeo Tasso organized 32 of his relatives into the Company of Couriers (Compagnia dei Corrieri) and linked Milan with Venice and Rome. The recipient of royal and papal patronage, his post riders were so comparatively efficient that they became known as bergamaschi throughout Italy.

Ruggiero de Tassis was named to the court of the Emperor Frederick the Peaceful in 1443. He organized a post system between Bergamo and Vienna by 1450; from Innsbruck to Italy and Styria around 1460; and Vienna with Brussels around 1480. Upon his success, Ruggiero was knighted and made a gentleman of the Chamber. Janetto von Taxis [de] was appointed Chief Master of Postal Services at Innsbruck in 1489. Philip of Burgundy elevated Janetto's brother Francesco I de Tassis [it] to captain of his post in 1502. Owing to a payment dispute with Philip, Francisco opened his post to public use in 1506. In 1512 the family was ennobled by Emperor Maximilian I. By 1516, Francisco had moved the family to Brussels in the Duchy of Brabant, where they became instrumental to Habsburg rule, linking the rich Habsburg Netherlands to the Spanish court. The normal route passed through France, but a secondary route across the Alps to Genoa was available in times of hostility.

At the death of Francisco in 1517, Emperor Charles V appointed Francisco's nephew Johann Baptista von Taxis (1470-1541) as Generalpostmeister of the Kaiserliche Reichspost. Johann Baptista was briefly succeeded by his eldest son, Franz II von Taxis (1514-1543), after whose untimely death the family split into two further branches. The youngest son, Leonhard I von Taxis, succeeded as Generalpostmeister and is the ancestor of the princely Thurn and Taxis family. Johann Baptista's second-eldest son, Raymond de Tassis (1515-1579), took over the office of postmaster-general to the Crown of Spain and settled in Spain. Raymond married into Spanish nobility, and his eldest son Juan de Tassis was created Count of Villamediana in 1603 by Phillip III. The Spanish line of the family became extinct with Juan de Tassis, 2nd Count of Villamediana, a poet who died in mysterious circumstances in 1622. A sister of Johann Baptista, Elisabeth Taxis, and her husband Bonus of Bordogna, founded the Taxis-Bordogna-Valnigra family, whose descendants held the office of Lieutenant Postmaster General in the Trento and Alto Adige regions through a later baronial line, and that of Lieutenant Postmaster General in Bolzano through a comital line.