Hacksjön is a small lake located east of the former airport at Tullinge, in the municipality Botkyrka in southern Stockholm, Sweden.

With its isolated location surrounded by moorlands and forests, the lake remains relatively unaffected by human activities, which is mostly limited to precipitation and incoming nutrients from local soil.

Additionally, the area is considered as of significant archaeological interest since it 8.000 years ago, during the Stone Age, was an archipelago composed of sparsely scattered islands and thus contains many traces of the earliest settlements in Stockholm.

The area between the lake and the golf course south of it is considered as of great importance for social history since the homestead there is believed to be about 1.500 years old.

[4] Open-air and motor sport activities have driven away a range of birds species once abundant by the lake, including the colony of black-headed gulls which once dominated it, other common species such as pochard, common teal, mute swan, Eurasian coot, and more rare visitors such as osprey and black-throated diver.