Milseburg, Mountain and archaeological site in Rhön Mountains, Germany.

Milseburg is an 835.2 m high mountain in the Kuppenrhön, the highest point of that part of the Rhön, in the municipality of Hofbieber in Hesse. Its summit is a phonolite body, not basalt, pushed up through Buntsandstein and left standing about 130 m above the surrounding land. The upper slopes are bare and rocky, below them dense forest, with pasture at the foot.

The hill was already recorded as Milsiburg in a document issued by Emperor Otto II on 25 July 980, marking a border between the Fulda monastery and the Hünfeld district. The Celtic oppidum on the northwest slope was occupied from the 6th/5th century BC to the 1st century BC; its rampart, up to twelve metres wide at the southeast foot, was reconstructed in 2003/2004 and is explained on panels. A small castle on the Liedenküppel spur, just 21 by 24 metres, is first mentioned in 1119 and was abandoned by the 13th century.

The Gangolfskapelle is a small pilgrimage chapel honouring Saint Gangulphus, built near the spot where the Celtic sanctuary is presumed to have stood. Beside it a stone pulpit allows open-air preaching. The name of the hill comes from a legend in which the giant Mils, allied with the devil, was defeated by Gangulphus; the devil then heaped stones over the body, forming the mountain.

The easiest access is from the northwest, the only side without steep slopes; other approaches climb through scree and forest. The summit plateau measures about 450 by 275 metres, and springs there once supplied the Celtic residents. The L 3379 between Kleinsassen and Oberbernhards passes just north of the mountain, with a side road branching east to Danzwiesen.

The main rampart was long mistaken for a modern field boundary, so when the railway was built in 1896 much of the northern wall was dug away for gravel. Rudolf Virchow had already recognised its ancient origin; in 1906 Ch. L. Thomas identified it as a post-slot wall (Pfostenschlitzmauer).