Erstavik, Manor estate in Nacka Municipality, Sweden.

Erstavik is a manor house in Nacka Municipality, south of Stockholm, at an inlet of the Baltic Sea. The main building, designed by Jean Eric Rehn and completed in 1765, is a three-storey brick structure with a plastered facade, projecting central risalit and a hipped, mansard roof. It is flanked by two lantern-topped wings, one of which houses the chapel.

Erstavik is first mentioned in 1356 as the seat of Bengt Larsson. In 1717 it was bought by councillor Olof Törnflycht, whose widow lived there until 1762. In 1763 merchant Herman Petersen, a director of the Swedish East India Company, acquired the estate and had Jean Eric Rehn rebuild the main building between 1763 and 1765. Petersen died in 1765; his will made Erstavik a fideicommissum for his eldest son Johan Abraham, and the estate stayed in the af Petersens family until 2015.

The property is managed under a traditional inheritance system that has become rare in Sweden. This old way of handling estates shapes how the place looks and is cared for today.

The estate is best explored on foot using the pathways that wind through the nature reserve. Visit during dry weather when the trails are in good condition for walking.

Erstavik was a fideicommissum from 1763 to 2015, when the last holder, Johan af Petersens, died and the government allowed the land to pass to Herman Petersen Fideikommiss AB. The Fideikommissnämnd then permitted the estate to be divided, ending the arrangement.