Harlyberg, Mountain summit in Lower Saxony, Germany.

The Harlyberg is the 255.9 m high summit of the Harly, a wooded ridge about 6.5 km long and 1.5 km wide in the northern Harz foreland, mostly in the district of Goslar. The ridge runs west-northwest to east-southeast and was formed by halokinesis as part of the Vienenburg saddle. On the summit stands the Harlyturm observation tower; the Kammweg runs along the crest.

The Harlyberg's east-southeast end above the Okertal was the site of the Harliburg, built in 1203 by King Otto IV. After his death the castle's heirs used its position for raids and highway robbery, so it was besieged for several months in 1291 and then completely razed. The Harlyturm on the summit, also called the Napoleonturm, was restored and reopened to tourists in 1986 after decades of decay.

The name Harly is also recorded as Harli and Harliberg. The forest is a near-natural hillside wood on dry, warm limestone and silicate soils. The Harlyturm is also called the Napoleonturm, and it is open when a flag flies above its roof.

The summit is reached on forest tracks and hiking trails through the Harly Forest, for example the Kammweg ridgeway; the Harly-Rundwanderweg 3 runs along the southwest slope. Access roads branch off the B 82 west of the ridge and the B 241 near Vienenburg, and the L 510 links both between Weddingen and Vienenburg. The Harly Tower is open when a flag flies above its roof.

The tower is also called the Napoleonturm. It stands on the summit itself, not on the slopes, and is open only when a flag flies from its roof. From the platforms the Harz lies south, the Elm north and the Huy east.