Bridegroom's Oak, Ancient oak tree in Dodauer Forst, Germany

The Bridegroom's Oak is a tree in the Dodauer Forst woodland of Schleswig-Holstein, known for a hollow opening in its trunk. This cavity sits roughly 3 meters (10 feet) off the ground and can be reached by climbing a small ladder.

In 1891, a man and woman started leaving letters for each other inside the hollow because their families opposed the relationship. After winning over their parents, the couple held their wedding under the branches.

The tree serves as a meeting point for people looking for companionship, with strangers opening letters and writing back if they feel a connection. Anyone who finds a message inside the trunk can reply and start a conversation.

The tree receives mail six days a week, and letters pile up inside the hollow until someone climbs the ladder to read them. Visitors are free to open any letter they find and take it with them if they wish.

On 25 April 2009 the oak was symbolically married to the Himmelgeist Chestnut, a horse-chestnut in Düsseldorf and the second tree in Germany with its own postal address. The pairing ended six years later when the chestnut died in 2015 and its trunk was turned into a sculpture.