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 chart plotter.

AIS is intended to assist the vessel's watchstanding 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.).

Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz.

It is also known as the meter band or meter wave as the wavelengths range from ten to one meters. Frequencies immediately below VHF are denoted HF, and the next higher frequencies are known as Ultra high frequency (UHF).

A Vessel Traffic Service (VTS) is a marine traffic monitoring system established by harbor or port authorities, similar to air traffic control for aircraft.

Typical VTS systems use radar, CCTV (closed-circuit television), VHF radiotelephony and AIS to keep track of vessel movements and provide navigational safety in a limited geographical area.