Claude Jager, born in 1940 in Elvange, Moselle, is a French mountaineer and guide. He discovered the mountains during his studies at the National Institute of Applied Sciences in Lyon, where he befriended climbers such as Marc Martinetti, Jean-Paul Paris, and Yannick Seigneur, with whom he completed his first mountaineering expeditions. An aspiring guide since 1964, he opened numerous new routes in the following years. Appointed a teacher at the Lycée du Fayet, he met Walter Cecchinel, with whom he completed a series of remarkable winter ascents.

His career is marked by major achievements, including the first ascent of the northeast couloir of Les Drus, made with Walter Cecchinel from December 28 to 31, 1973. This route, considered one of the most difficult in the Alps, is a steep ice couloir, exposed to avalanches and framed by vertical slabs. The feat was hailed at the time as a technical achievement and a pinnacle of winter mountaineering. Claude Jager also participated in the French expedition to the west pillar of Makalu (8,481 m) in 1971, led by Robert Paragot. This expedition marked the history of Himalayan mountaineering by opening a new route on one of the world's highest peaks, in extreme weather conditions and at the cost of total physical and mental dedication.

Alongside his guiding activities, Claude Jager worked as a high school teacher, passing on his passion for the mountains to many young people. After a rich and committed career, he settled in Chamonix, where, at over 80 years old, he continues to explore the trails and contemplate the peaks that have marked his life as a mountaineer.