A self-tapping screw is a type of screw that can be tapped because it is driven into its own hole in the material. More narrowly speaking, self-tapping is only used to describe a specific type of thread cutting screw used to produce threads in relatively soft materials or plates, with the exception of wood screws. Other specific types of self-tapping screws include self-drilling screws and threaded screws.

Self-tapping screws have a wide range of tips and thread styles, and can be used in almost any possible screw head design. The common feature is that the thread covers the entire length of the screw from the tip to the head, and the obvious thread is hard enough for the intended substrate, usually case hardened.

For hard substrates such as metals or hard plastics, the self-tapping ability is usually produced by cutting gaps in the thread continuity on the screw, resulting in grooves and cutting edges similar to those on a tap. Therefore, ordinary machine screws cannot tap and tap holes on the metal substrate, but self-tapping screws can (within the reasonable range of the hardness and depth of the substrate).

For softer substrates (such as wood or soft plastic), the self-tapping ability can simply come from a tip that tapers to the gimlet point (no groove required). Just like the tip of a nail or hand drill, such a point creates a hole through the displacement of the surrounding material instead of any chip-forming drilling/cutting/evacuation action.

Not all self-tapping screws have sharp points. The B-type tip is blunt and is intended to be used with pilot holes, often in sheets. The lack of a sharp tip facilitates packaging and handling, and in some applications may help reduce the clearance required to fasten the back of the panel or provide more threads on a screw of a given length.