A credit union is a member-owned financial cooperative, democratically controlled by its members, and operated for the purpose of promoting thrift, providing credit at competitive rates, and providing other financial services to its members.

Many credit unions also provide services intended to support community development or sustainable international development on a local level, and could be considered community development financial institutions.

Worldwide, credit union systems vary significantly in terms of total system assets and average institution asset size, ranging from volunteer operations with a handful of members to institutions with several billion dollars in assets and hundreds of thousands of members.

Credit unions differ from banks and other financial institutions in that the members who have accounts in the credit union are the owners of the credit union and they elect their board of directors in a democratic one-person-one-vote system regardless of the amount of money invested in the credit union.