A whip is a tool or weapon designed to strike humans or animals to exert control through pain compliance or fear of pain. They can also be used without inflicting pain, for audiovisual cues, such as in equestrianism. They are generally either a firm stick designed for direct contact, or a flexible line requiring a specialized swing. The former is easier and more precise, the latter offers longer reach and greater force. A hunting whip combines a firm stick (the stock or handle) with a flexible line (the lash or thong).

Whips such as the "cat o' nine tails" and knout are specifically developed for flagellation as a means of inflicting corporal punishment or torture on human targets. Certain religious practices and BDSM activities involve the self-use of whips or the use of whips between consenting partners. Misuse on animals may be considered animal cruelty, and misuse on humans may be viewed as assault.