The Hagen Mountains () are a mountain range over 3,000 metres high in Papua-New Guinea, in the northeast of the island of New Guinea. The range lies on the territory of the former German colony of German New Guinea in the Kaiser-Wilhelmsland, west of and parallel to the middle Ramu valley. It was discovered in 1896 and named after , then director general (Generaldirektor) of the New Guinea Company and governor of German New Guinea. Curt von Hagen's father was the royal adjutant and lieutenant-general, Heinrich von Hagen; Curt von Hagen was thus a great grandson of the polymath, Karl Gottfried Hagen, of Königsberg.
The Hagen Mountains are a relatively compact massif of volcanic origin. Their highest peak is the 3,778-metre-high Mount Hagen (Hagensberg), after which the town of Mount Hagen, 25 kilometres to the southeast, is named.