Kaiserliche Reichspost (German: [ˈʁaɪçsˌpɔst], Imperial Mail), originally named Niederländische Postkurs (Low Countries' postal route), was the name of the postal service of the Holy Roman Empire, founded in 1490. Often considered the world's first modern postal service, it initiated a revolution in communication in Europe.

In the late 15th and early 16th century, the Habsburg dynasty had managed to develop a transoceanic empire, on which it was said that "The sun never sets", but unlike the ancient Romans and Persians or their contemporary Chinese, Russians, Aztecs, or Incas, they lacked the financial capacity to maintain a postal system on their own. Other European governments tried to develop their own models as well, but efforts usually proved short-lived, as in the case Louis XI's ambitious project.

It was founded by the brothers Janetto and Francesco Tasso (Franz von Taxis) together with Maximilian of Austria in 1495, on the basis of the pre-existing Italian models and the courier networks built by Frederick III and Charles the Bold. The Bergamascan Tasso family had built up postal routes throughout Italy since c. 1290 and Jannetto's uncle^{[citation needed]} Ruggiero had worked for Frederick III since the mid-15th century.

After the marriage of Archduke Maximilian of Austria and Mary of Burgundy, to have a better line of communication to govern the Habsburgs' scattered territories, Maximilian commissioned the Taxis to organize the first postal line from Mechelen to Innsbruck. Maximilian's son Philip, as Duke of Burgundy and King of Castile, expanded the Habsburg postal system established by his father. In 1500, the centre of the system was transferred to Brussels by Franz von Taxis, whom Philip made his postmaster-general. At first, urged by his father, Philip tried to take over the system, but he realized that his bureaucrats were unable to run it efficiently. Thus he made an agreement (later renewed by Charles of Burgundy) with the Taxis that allowed them to operate unhampered by interference from the state, as long as they maintained standards in accordance with the Habsburgs' interests. On January 18, 1505, Philip unified communication between Germany, the Netherlands, France and Spain by adding stations in Granada, Toledo, Blois, Paris and Lyon. Charles of Burgundy, later Charles V, continued to develop the system after his father's death. Behringer notes that, "Whereas the status of private mail remains unclear in the treaty of 1506, it is obvious from the contract of 1516 that the Taxis company had the right to carry mail and keep the profit as long as it guaranteed the delivery of court mail at clearly defined speeds, regulated by time sheets to be filled in by the post riders on the way to their destination. In return, imperial privileges guaranteed exemption from local taxes, local jurisdiction, and military service. The terminology of the early modern communications system and the legal status of its participants were invented at these negotiations." He confirmed Jannetto's son Giovanni Battista as Postmaster General (chief et maistre general de noz postes par tous noz royaumes, pays, et seigneuries) in 1520. By Charles V's time, "the Holy Roman Empire had become the centre of the European communication(s) universe."

Augsburg benefitted majorly from the system. Even when the Habsburg empire began to extend to other parts of Europe, Maximilian's loyalty to Augsburg, where he conducted a lot of his endeavours, meant that the imperial city became "the dominant centre of early capitalism" of the sixteenth century, and "the location of the most important post office within the Holy Roman Empire".

The system quickly converged with the European trade system and an emerging market for news. According to Behringer, "During the reign of Emperor Maximilian, when private use of the imperial posts was still illegal, the terminuses of the first transcontinental post lines were already shifted from Innsbruck to Venice in the south, and from Brussels to Antwerp in the north. News arrived from all over the world in these towns, and this is where the communication and news businesses started to merge. And even more importantly, the Fuggers and other trading companies had their most important branches in these ports."

Confirmed by Emperor Rudolph II in 1595, the Imperial postal service remained a monopoly of the Thurn und Taxis family (officially hereditary from 1615 onwards) until it was terminated with the end of the Empire in 1806.

The Imperial Reichspost was first based in Mechelen, before being moved to Brussels in the Netherlands, from where the original ("Dutch") route led via Namur, Bastogne, Lieser, Wöllstein, Rheinhausen, and Augsburg to Innsbruck and Trento. It was also used to bypass the Kingdom of France in order to keep in touch with Habsburg Spain during times of hostility. Brussels was the side that organized and paid for the system.