The Automatic Identification System (AIS) is a system used by ships and Vessel Traffic Services (VTS) principally for identification and locating vessels. AIS provides a means for ships to electronically exchange ship data including: identification, position, course, and speed, with other nearby ships and VTS stations. This information can be displayed on a screen or an ECDIS display. AIS is intended to assist the vessel's watch standing officers and allow maritime authorities to track and monitor vessel movements. It works by integrating a standardized VHF transceiver system with an electronic navigation system, such as a LORAN-C (LOng RAnge Navigation Version C) or Global Positioning System receiver, and other navigational sensors on board ship (gyrocompass, rate of turn indicator, etc.).

The International Maritime Organization's (IMO) International Convention for the Safety of Life at Sea (SOLAS) requires AIS to be fitted aboard international voyaging ships with gross tonnage (GT) of 300 or more tons, and all passenger ships regardless of size. It is estimated that more than 40,000 ships currently carry AIS class A equipment.