Isidorus is a lunar impact crater that is located to the north of the Mare Nectaris, on the eastern half of the Moon's near side.

[1] It forms a pair with the slightly larger Capella, which is attached to the east-northeastern rim.

The interior floor has been resurfaced by lava and is generally level, although it is marked by the small, bowl-shaped crater Isidorus A along the western rim.

There is a tiny remnant of a craterlet attached to the northern rim of the latter formation.

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