Battered woman syndrome concept was introduced in the 1970s by Lenore Walker to elucidate battered women's experiences and behaviors. Although not technically a legal defense, battered woman syndrome has been used in the criminal justice system. One of its well‐known uses is in self‐defense cases of battered women who have killed their abusive partners. This entry discusses the two main theories used to support battered woman syndrome, namely the cycle theory and learned helplessness. The ways in which battered woman syndrome has been used within the criminal justice system is discussed. Furthermore, early landmark cases used in courts for battered woman syndrome are examined. Finally, this entry provides an overview of battered woman syndrome's beneficial and damaging legal applications as well as some of the major criticisms directed at its use generally.