The Helmbach is an 11 km (6.8 mi) long tributary of the Speyerbach stream in the Palatine Forest in the German state of Rhineland-Palatinate.

The stream rises northwest of the Taubensuhl Forester's Lodge (Forsthauses Taubensuhl) and flows initially 4 km (2.5 mi) in a northeasterly direction to the Geiswiese meadow.

There it is joined on the left by the Blattbach, which rises on the north slopes of the 551 m above NN high Blattberg hill, and then heads in an easterly to northeasterly direction.

[3] There the stream is joined by the Grobsbach and, 2.5 km (1.6 mi) further on, the Iggelbach empties into it from the left.

Here it is joined on the right by the Kohlbach, which has been impounded to create the reservoir of Helmbachweiher a little to the east.