Geilo (or Geylo, French Gilon) (died 28 June 888) was the Bishop of Langres from 880 until his death. His episcopate coincided mostly with the emperorship of Charles the Fat and after 885 he is a leading ecclesiastical figure at the imperial court. Geilo increased the landholdings and comital rights of the diocese of Langres immensely in his short tenure, a sign of political sagacity. Geilo has been painted as a villain, an amibitious prelate trying to extend his see's temporal authority as far as it could go under the reign of weak Carolingians.
Geilo was the son and namesake of Count Geilo. He was the abbot of Flavigny from 866 until 870, and of Tournus during the last years of the reign of Charles the Bald. In 879, he crowned Boso of Provence in Mantaille; Boso in turn made him Bishop of Langres. He quickly changed sides and supported Carloman II in 880, being confirmed in his diocese, and even staying with the king at the siege of Vienne throughout the year.
When Carloman died in 884, Geilo was instrumental in bringing Charles the Fat to the throne in West Francia. It is likely that he in fact crowned Charles rex in Gallia on 20 May 885 at Grand in his diocese. Geilo even developed a special West Frankish seal for Charles and met him at the Siege of Paris in 885.
Geilo is a centre in the municipality of Hol in Norway, in the valley of Hallingdal, with around 2,300 inhabitants. The Bergen Line facilitated Geilo's development as the first skiing resort in the country, and it is still one of the largest. It is also famous for having some of the most luxurious and expensive holiday cabins in Norway.
Geilo is primarily a ski resort town, but also offers summer activities. Geilo is in a valley with mountain ranges on each side. The center of the town lies at 800 meters above sea level, and its highest point is 1178 meters above sea level. It is 250 km from Oslo and 260 km from Bergen.
It has a train station (Geilo stasjon) with roughly five trains a day going to either Bergen (to the west) or Oslo (to the east). The closest airport is Geilo Airport, Dagali (24 km away), while the closest airport that accepts international flights is Fagernes Airport. Geilo has three lakes, Slåttahølen, Vestlefjorden, and Ustedalsfjorden, by far the largest of the three.