Himmelgeister Kastanie, Natural monument site in Himmelgeist, Düsseldorf, Germany

The Himmelgeister Kastanie was a horse chestnut tree standing in open fields just outside the Himmelgeister Rheinbogen nature reserve in Düsseldorf-Himmelgeist. Declared a natural monument in 1997, it was felled in December 2015, leaving a 5-metre stump that chainsaw artist Jörg Bäßler carved into a tree-spirit sculpture. This stump was removed in October 2024 because it had become rotten.

The horse chestnut, estimated 150 to 200 years old, was declared a natural monument by the city of Düsseldorf in 1997. In 2006, after a disease threatened it with felling, walkers formed the Baumgeister group and collected signatures to save it. A storm in November 2015 broke an eight-metre branch, and on 14 December 2015 the crown was removed, leaving a five-metre trunk. Chainsaw carver Jörg Bäßler turned this stump into a tree-spirit sculpture, which was removed in October 2024 because it had become rotten.

In April 2007 the tree received its own official postal address from Deutsche Post, with a mailbox and daily delivery, making it Germany's second tree after the Bräutigamseiche in Eutin to have one. Volunteers from the Freundeskreis der Himmelgeister Baumgeister answered the mail in the name of Jüchtwind, a tree spirit said to live in the chestnut. On 25 April 2009 the chestnut and the Eutin oak were symbolically married.

The location sits easily accessible along a Rhine bend in the southern part of the city and can be reached on foot or by bicycle. The site is open and can be visited anytime without special arrangements needed.

On 25 April 2009 the chestnut was symbolically married to the Bräutigamseiche, a bridegroom oak in the Dodauer Forst near Eutin. The pairing linked two trees that both held official German postal addresses. The tree's own address, "Baumgeist, Himmelgeister Kastanie, Kölner Weg, 40589 Düsseldorf", was granted in April 2007, second in Germany after the Eutin oak.