Helmholtz is a lunar impact crater, approximately 110 kilometers in diameter, that is located near the south-southeast limb of the Moon.

Attached to the south-southeast rim of Helmholtz is the somewhat smaller crater Neumayer.

The northern half of the interior floor is level and marked only by a few very tiny craterlets.

The southern floor is more irregular due to the overlaying ejecta from Neumayer and Boussingault, and is marked by a pair of tiny craters in the southeast.

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