A shift knob also known as a gear knob, gear shift knob and stick shift knob is the physical interface between the manual transmission stick shift and the drivers hand. Made of many materials from simple plastics through to platinum it comes in many shapes sizes and weights. Generally spherical in shape the OEM versions tend towards the conservative and the automotive aftermarket versions can be found to be of very original design.

The shift knob's principal function is the ergonomical interface between driver and the manual transmission stick shift. The stick shift, as the name implies, is often just a machined or cast aluminium or steel rod with or without threading the shift knob is fitted on its end.

In recent years manufacturers have increased the variety of shifts knobs available to the consumer from inexpensive plastics to diamond studded white gold.

A weighted shift knob is a performance driven aftermarket modification which entirely replaces the OEM shift knob and sits atop the aftermarket short shifter or OEM manual shift stick. Initially designed to be used in tandem with a short shifter, it is increasingly being purchased for stock stick shifts. The weight generally varies between 400 and 600 grams or more, depending on the material used. The principle of the weighted shift knob is to make the stick shifter top heavy, thus increasing the available leverage in order to decrease time between shifts. Weighted gear knobs are offered for sale by a variety of North American based manufacturers in many shapes and finishes, though they are significantly more expensive than the commonly available aftermarket shift knob.