A wristlock is a joint lock primarily affecting the wrist-joint and, in some cases, the radioulnar joints through rotation of the hand. A wristlock is typically applied by grabbing the opponent's hand, and bending and/or twisting it. Wristlocks are very common in martial arts such as aikido, hapkido and jujutsu where they are featured as self-defense techniques. They are also used as submission holds in martial arts such as Brazilian jiu-jitsu (where the most common name is mão de vaca, "the cow's hand") and catch wrestling. While being an illegal technique in modern sambo and judo competitions, it is still practiced in judo forms of self-defense kata kōdōkan goshinjutsu. Wristlocks are also widely used as pain compliance holds, often in police, military, and residential treatment centers.

The wristlock is a technique that can be applied from a stand-up position, simply by grabbing the opponent's hand and twisting and/or bending it in a non-natural direction. It is considered to be a relatively safe technique to practice with a willing opponent, but if applied suddenly and/or forcefully, a wristlock can cause ligament tears or possibly even dislocation or bone fractures.

Mixed martial arts (MMA) organizations usually allow wrist locks, but they are rarely performed as a result of the grappling gloves and wrist wraps typically worn by MMA fighters, which both restrict the movement of the wrist. Wrist locks are seen as being easy to defend against, and often leave the attacker vulnerable to punches and elbow strikes.