A straitjacket is a garment shaped like a jacket with overlong sleeves and is typically used to restrain a person who may otherwise cause harm to him/herself or others. Once the arms are inserted into the straitjacket’s sleeves, they are then crossed across the chest. The ends of the sleeves are then tied to the back of the wearer, ensuring that the arms are kept close to the chest with as little movement as possible.

Although straitjacket is the most common spelling, strait-jacket is also frequently used, and in Scotland strait-waistcoat, which is generally deemed archaic. Straitjackets are also known as camisoles.

The straitjacket’s effectiveness as a restraint makes it of special interest in escapology. The straitjacket is also a staple prop in stage magic and is sometimes used in bondage games.

The negative connotations of the straitjacket as an instrument of torture come from the earlier Victorian era of medicine. Physical restraint was then extensively used both as treatment for mental illness and as a means of pacifying patients in understaffed asylums.

Due to the strength of the material, canvas or duck cloth is often used for making institutional straitjackets. However, leather or PVC is most often used for recreational or fashion wear.

The term is used metaphorically, as in the phrase “intellectual straitjacket” to criticize very tight boundaries on what ideas are allowed, as imposed by an ideological system of thought.