Winthrop is the remnant of a lunar impact crater that has been flooded by lava from the Oceanus Procellarum.

It was named after American astronomer John Winthrop.

[1] It lies across the western rim of the much larger crater Letronne, a feature that has been nearly destroyed by the intruding mare lavas.

All that survives of Winthrop are a few segments of the outer rim.

Winthrop was previously identified as Letronne P before being renamed by the IAU in 1976.