Ekumen

Ekumen is the fictional galactic federation of human-inhabited worlds mentioned in several of the science fiction novels of Ursula K. Le Guin.

In keeping with Le Guin's soft science fiction style, the setting is used primarily to explore anthropological and sociological ideas. The Ekumen worlds are some dozens of planets populated millions of years ago by human beings from the original human world of Hain. The Hainish did not scruple to use genetic engineering techniques to adapt human beings to non-optimal worlds (for example the androgynes of Gethen in The Left Hand of Darkness).

Hainish civilization subsequently collapsed and the colony planets forgot that other human worlds existed. The Ekumen stories tell of the renewal of interplanetary travel and communication and the efforts to re-establish a galactic "federation".

Especially notable (award-winning) Ekumen novels include The Left Hand of Darkness and The Dispossessed.
Others are Rocannon's World and The Telling.