Naonobu is a small lunar impact crater that is located on the eastern Mare Fecunditatis, to the northwest of the prominent Langrenus crater. It forms a triple-crater formation with the adjacent Atwood crater to the south and Bilharz crater just to the southwest. Naonobu and Atwood craters are only separated by a gap of a few kilometers wide.

The interior of this crater has been flooded with basaltic-lava, leaving a relatively flat interior and a reduced outer rim. There is no central peak, but a tiny craterlet lies just to the southwest of the mid-point. A similar craterlet lies across the western interior of the rim.

This crater was previously designated 'Langrenus B' before being renamed by the IAU.