Know your customer (KYC) is the bank regulation specifying the due diligence that financial institutions and other regulated companies must perform; it requires that they identify their clients and collect information relevant to doing business with them.

The US government has implemented KYC as part of the Bank Secrecy Act and the USA PATRIOT Act. KYC policies are used to prevent identity theft and money laundering, and they are an important tool for disrupting the funding of terrorism. KYC entails much more than just filling out forms; it is a process that touches every aspect of a customer relationship.

Banks that perform KYC monitoring for anti-money laundering (AML) and Counter-Terrorism-Financing (CTF) purposes often use specialised transaction-monitoring software designed to analyse names and monitor trends.