Definition: Card issuer
In the case of four-party schemes, a credit institution (or more rarely, another undertaking) which is a member of a card scheme and has a contractual relationship with a cardholder that results in the provision and use of a card from that card scheme. In the case of three-party schemes (e.g. American Express, Diners Club International, etc.), the card issuer is the card scheme itself.
European Central Bank, Guideline of the European Central Bank of 1 August 2007 on monetary, financial institutions and markets statistics (recast), Official Journal of the European Union No L 341, 27.12.2007, p. 1 - 232