Seleucus is a lunar impact crater located in the western part of Oceanus Procellarum.

To the west is the lava-flooded remains of the walled plain Eddington.

A bright ray from Glushko crater, about 500 km to the southwest, grazes the southeastern rim of Seleucus.

The narrowness of the rim of Seleucus and the abrupt contact between its raised rim and the surrounding mare prove that the final mare flooding occurred after the crater was formed, and so the crater is older than the youngest (uppermost) mare basalts in the vicinity.

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Seleucus.