Post Office Tree, Mossel Bay, Ancient milkwood tree landmark in Mossel Bay, South Africa.

The Post Office Tree is a milkwood (Sideroxylon inerme) in the grounds of the Bartholomeu Dias Museum Complex on Market Street, Mossel Bay. It stands near the spring from which Bartolomeu Dias drew water, and a boot-shaped post box has been placed beneath it; letters posted there are franked with a commemorative stamp.

In 1501 Portuguese navigator Pêro de Ataíde, sheltering in Mossel Bay after losing much of his fleet in a storm, hung a report of the disaster in an old shoe from a milkwood tree near the spring where Bartolomeu Dias had drawn water. João da Nova, the addressee, found it, and the tree served as a de facto post office for decades. Da Nova erected a small shrine nearby, considered the first place of Christian worship in South Africa.

The tree served as a communication hub between European sailors and local people along the South African coast during the age of exploration. This exchange of messages between cultures continues today when visitors use the boot-shaped post box beneath its branches.

The tree stands in the grounds of the Bartholomeu Dias Museum Complex on Market Street, about 330 km east of the Cape of Good Hope. Letters posted in the boot-shaped box beneath it are franked with a commemorative stamp. The complex charges an entrance fee.

João da Nova, the explorer who found Pêro de Ataíde's report, built a small shrine beside the tree; though no trace survives, it is regarded as the first place of Christian worship in South Africa. Letters posted in the boot-shaped box today are franked with a commemorative stamp.