A check or cheque is a document instructing a financial institution to pay a specific amount of a specific currency from a specific current account held in the issuer's name with that institution. Both the issuer and payee may be individuals or commercial entities.

An order check—the most common form in the United States—is payable only to the named payee or his endorsee. A bearer check—the most common form in Europe—is payable to anyone who is in possession of the document, although checks are often crossed a/c payee to restrict payment to the payee.

In games such as chess, shogi and xiangqi, a check is an immediate threat to capture the king. A king so threatened is said to be in check.