The Oppidum of Manching (Oppidum von Manching) was a large Celtic proto-urban or city-like settlement at modern-day Manching, near Ingolstadt, in Bavaria, Germany. The Iron Age town (or oppidum) was founded in the 3rd century BC and existed until c. 50-30 BC. It reached its largest extent during the late La Tène period (late 2nd century BC), when it had a size of 380 hectares. At that time, 5,000 to 10,000 people lived within its 7.2 km walls. Thus, the Manching oppidum was one of the largest settlements north of the Alps. The ancient name of the site is unknown, but it is assumed that it was the central site of the Celtic Vindelici tribe.
The enormous circular fortification around the site survived the demise of the settlement as a visible landscape feature. It had already been noted by the Romans (see below); for centuries it remained an important landmark e.g. for the boundaries of parishes or bishoprics. A first description was penned by the schoolteacher J.A. Buchner (1776–1854) in 1831, under the erroneous assumption of having found the Roman site of Vallatum. First excavations took place in 1892-93 under Joseph Fink (1859–1929). In 1903, Paul Reinecke recognised the site as a Celtic oppidum.
In 1936–38, during the Nazi remilitarisation of Germany, the Luftwaffe constructed an airfield at Manching. This led to the destruction of large proportions of the site; without providing the opportunity for systematic archaeological research. Only very few finds were recovered from the construction site. In 1938, the archaeologist Karl-Heinz Wagner started an excavation of the northeast part of the enclosure. Within the visible earthen bank, he discovered the remains of a wall, which he described as a murus gallicus according to Julius Caesar's description of such structures. Due to the presence of the airfield, Manching was the target of multiple bombing raids during World War II, leading to further destruction of archaeological evidence.