Dowsing, sometimes called divining or water witching, refers to practices which some people claim enables them to detect hidden water, metals, gemstones or other objects, usually obstructed by land or sometimes located on a map. Most commonly, the movement or vibrations of apparatus, such as a Y-shaped twig, an L-shaped rod or a pendulum, is used in the practice. Some practitioners use no apparatus at all.

The efficacy of dowsing is not accepted by the general scientific community. Some researchers believe there is evidence to support it. Many people believe that it works, and it is widely practiced in its various forms.

Many dowsers use simple brass rods bent in an "L" shape known as divining rods; others use wooden Y-rods and/or even bent wire coat hangers. According to some dowsers who use divining rods, brass allows the rod to attune to magnetic fields emanated by the target without the earth's EM field interfering, as would be the case with a metal such as steel. The end of the rod to be held by the dowser is often encased in a material that provides a constant electrical impedance, to prevent the dowser's own conductivity from interfering with the dowsing process.

Pendulums (these may be a crystal suspended on a chain, or a metal weight) can be used in divination and dowsing. In one approach the user first determines which direction (left-right, up-down) will indicate "yes" and which "no," before proceeding to ask the pendulum specific questions. In another form of divination, the pendulum is used with a pad or cloth that has "yes" and "no" written on it, and perhaps other words, written in a circle in the latter case. The person holding the pendulum aims to hold it as steadily as possible over the center. An interviewer may pose questions to the person holding the pendulum, and it swings by minute unconscious bodily movement in the direction of the answer. In the practice of radiesthesia a pendulum is used for medical diagnosis.

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