A submission is a technique in Brazilian Jiu-Jitsu that requires the opponent to admit defeat by "tapping out" (or simply "tapping") to avoid injury. These techniques work primarily either by twisting, locking, or hyperextending a joint, or by choking techniques that may render the opponent unconscious. The practice of tapping allows these techniques to be practiced safely, even when sparring, by stopping the technique before it can be finished. The student of BJJ is also careful to allow the opponent the opportunity to tap out rather than intentionally seeking to harm the opponent.

Effective submission techniques usually build off attaining a pinning technique, or control position, which makes the opponent unable to defend the application of the submission by removing the opponents freedom to move his body, especially his head, shoulders, hips, and legs. This leads to the phrase "position before submission", as without the control position, the submission technique may often be escaped or countered easily. This is why many other forms of jujutsu focusing on standing techniques are often far less effective than submissions in ground-fighting, as the opponent has too much freedom of movement of the rest of his body that can be used to neutralize such techniques. While submissions do exist and are often successfully applied in stand-up fighting, they tend to be much more effective on the ground due to the greater ability to achieve a dominant control position.