Johannser Kogel, Mountain summit in Lainzer Tiergarten, Vienna, Austria.

Johannser Kogel is a 377-meter summit located in the Lainzer Tiergarten in Vienna with dense oak forests covering its slopes. The area displays varied plant communities adapted to different conditions across the terrain.

The area was designated as a nature forest reserve in 1972 to protect its ancient woodland. Oak trees here are over 400 years old and grow following natural patterns.

The name comes from the Johannser Wald, first recorded in 1687 as St. Johann(s) Waldt after the Johanniterorden (Maltese Order), former owners of the area. The hill itself appears in documents in 1925 as Johannserkogel. Other local names, such as Johannser Schütt, Johannser Rennweg and Johannser Wiese, share this origin.

The Johannser Kogel lies in the Lainzer Tiergarten nature reserve in Hietzing, Vienna's 13th district. The 45-hectare core of the 70-hectare Naturwaldreservat is fenced off and closed to visitors of the Lainzer Tiergarten, so the old oaks cannot be reached on foot. The hill rises about 200 metres above the Wiental; the Rotwasser flows past its west and north sides.

Some oak trees in this forest area have trunk circumferences exceeding four meters, revealing their age and rarity. These massive trees form an important feature of the ancient woodland ecosystem.