The Royal Bavarian Auxiliary Corps (Greek: Βασιλικὸν Βαυαρικὸν Ἐπικουρικὸν Σῶμα, German: Königlich Bayerisches Hilfskorps) was a military force formed in 1832 to accompany the Bavarian prince Otto to the newly independent Kingdom of Greece, after he was chosen as the country's first king. As part of the treaty provisions of Otto's accession, a Bavarian-staffed volunteer military corps was to be formed to replace the forces maintained there by the Great Powers—chiefly the French troops of the Morea Expedition—as well as the remnants of the Greek forces organized during the Greek War of Independence, and provide cadres and training for the new Hellenic Army.

Because not enough volunteers could be found in time, regular Bavarian Army troops formed much of the actual corps that arrived with Otto in Greece in early 1833. The Bavarian Army regulars were gradually replaced by volunteers until 1834. These came chiefly from Bavaria, but also included men from diverse nations, and often of non-military background. Most of the Bavarians left by 1837, but many remained behind, dominating the Greek army and the administration. This "Bavarocracy" (Βαυαροκρατία), coupled with the huge expenses involved in maintaining the Bavarians, provoked great resentment among the Greeks, and was one of the chief causes of the 3 September 1843 Revolution.

Article 14 of the 1832 Treaty of London, where Britain, France, and Russia, agreed on the establishment of the Kingdom of Greece, under the Bavarian prince Otto, stipulated that Otto's father, King Ludwig I of Bavaria, would recruit a force of up to 3,500 soldiers, at the expense of the Greek treasury, to replace the allied troops (i.e., the French expeditionary corps). The latter would remain under the disposition of the King of Greece until the arrival of the Bavarian troops. In Article 15, the King of Bavaria promised to supply Bavarian officers for the establishment of a national army in Greece.

The Philhellene professor Friedrich Thiersch and Colonel Carl Wilhelm von Heideck, who had served in Greece under Governor Ioannis Kapodistrias and was now a member of Otto's regency council, reported on the situation in Greece to King Ludwig. Following the assassination of Kapodistrias in 1831, Greece was in near-constant civil war. The regular and irregular military forces organized by Kapodistrias were practically dissolved, but many thousands of their members retained their weapons and lived off the countryside. The Bavarians distrusted the irregular fighters who had fought the civil war, and wanted to avoid being drawn into the local factional struggles. Therefore, it was decided early on that Otto's new regime could rely solely on the Bavarian troops, who would enforce the new government's policies. To that end, all Greek military formations, chiefly composed of irregulars, would be disbanded, and Greeks were to be excluded from all senior positions in the administration and the military.

The expeditionary corps was formed following a convention concluded on 1 November 1832 between Karl von Abel, one of the three members of the projected regency for the underage Otto, on behalf of Greece and Philippe de Flad on behalf of the Kingdom of Bavaria.

The convention's 27 articles stipulated that the expeditionary corps of 3,500 men would be composed of staff, four infantry battalions, six cavalry companies, four artillery companies, and a technician company. The corps was to be composed of volunteers, but until these could be recruited, regular Bavarian Army troops would be provided; half of the corps were to stay in Greece for two years, and the rest for four; the mission of the Auxiliary Corps was slated to end on 1 January 1837. The costs for the maintenance of the corps were set at 50,000 florins annually, to be covered by the Greek government. Officers and adjutants were to receive pay equivalent to one rank above their own.

According to the Greek military historian Andreas Kastanis, the treaty contained "basic omissions" in terms of the corps' recruitment: First, the complete lack of a provision for engineering troops, which were an absolute necessity in war-ravaged and under-developed Greece. Indeed, for most of the 19th century the main occupation of Greek military engineers was building basic infrastructure across the country. Second, no formal requirements were placed for the Bavarian volunteers, and third, no requirements were placed for the Bavarian officers sent to oversee the training and organization of the nascent Hellenic Army.

Preparations for Otto's departure were confused, and little headway was made in the recruitment of the Auxiliary Corps before Otto was due to set out for Greece. As a result, King Ludwig was obliged to initially fill its ranks with troops seconded from the Bavarian Army: of the 3,582 men sent to Greece, about half were Bavarian Army regulars and the rest volunteers. The Bavarian Army units formed two combined regiments (one from 1st Battalion/6th Regiment [de] and 2nd Battalion/12th Regiment [de], and the other from 1st Battalion/10th Regiment [de] and 2nd Battalion/11th Regiment [de]), two light cavalry squadrons and eight field guns, under Brigade General Friedrich von Hertling. The Auxiliary Corps set out for embarkation at Trieste, while Otto left Munich on 6 December 1832 for Brindisi. On board the British frigate Madagascar, Otto joined the troop convoy at Corfu, but it took further two weeks of sailing through heavy weather before the fleet of 43 ships arrived at the Greek capital of Nafplion on 30 January 1833.