Home planet of Lt. Arex, the Enterprise navigator from 2269-70, and the tripodal Edosian race. Edos lies in the Triangulum constellation, on the rim of the galaxy. It is a jumping-off point for science teams studying the great energy barrier beyond the rim. It is also a peaceful planet which has never been involved in a war. The technology is as advanced as Earth's; the architectural style of its cities is strictly functional rather than aesthetically pleasing. The society has no class levels. All beings on Edos are equal.

Edos is not a member of the Federation. Rather, it remains in loose alliance with the Federation, coming under its agreements for trade, science, and aid in an emergency.

Because Edosians have a long life cycle, it is highly unusual for there to be more than one child per family, for the sake of keeping the population down. As a result, all children are precious, and families are close. Ancestral records are kept in great detail, dating back for centuries. For example, Arex's line can be traced for 3,000 years.