AOL Instant Messenger (AIM) is an instant messaging and presence computer program which uses the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time.

AIM became popular in the early 2000s in North America, and was the leading instant messaging application in that region. AIM's popularity steeply degraded at the end of the decade, and its fall has often been compared with other once-popular internet services such as MySpace.