In cryptography, a Certificate Authority or Certification Authority (CA) is an entity that issues digital certificates for use by other parties. It is an example of a trusted third party. CAs are characteristic of many Public Key Infrastructure (PKI) schemes.

Commercial CAs charge to issue certificates that will automatically be trusted by most web browsers (Mozilla maintains a list of at least 36 trusted root CAs, though multiple commercial CAs or their resellers may share the same trusted root).[1] The number of web browsers and other devices and applications that trust a particular certificate authority is referred to as ubiquity.

Aside from commercial CAs, some providers issue digital certificates to the public at no cost. Large institutions or government entities may have their own CAs.