Emergency position-indicating radiobeacon station (short: EPIRS) is – according to Article 1.93 of the International Telecommunication Union's (ITU) Radio Regulations (RR) – defined as «A station in the mobile service the emissions of which are intended to facilitate search and rescue operations.» In marine use the terminology Emergency Position Indicating Radio Beacon (EPIRB) is used.

EPIRB are tracking transmitters which aid in the detection and location of boats, aircraft, and people in distress. A PLB (personal locator beacon) is particular type of EPIRB that is typically smaller, has a shorter battery life and unlike a proper EPIRB is registered to a person rather than a vessel. The terms ELB (emergency locator beacon) and ELT (emergency locator transmitter) are used interchangeably with EPIRB only when used on aircraft. Strictly, they are radiobeacons that interface with worldwide offered service of Cospas-Sarsat, the international satellite system for search and rescue (SAR). When manually activated, or automatically activated upon immersion or impact, such beacons send out a distress signal. The signals are monitored worldwide and the location of the distress is detected by non-geostationary satellites doppler trilateration and in more recent EPIRBs also by GPS.

The basic purpose of a distress radiobeacon is to help rescuers find survivors within the so-called "golden day"(the first 24 hours following a traumatic event) during which the majority of survivors can usually be saved.

Since the inception of Cospas-Sarsat in 1982, distress radiobeacons have assisted in the rescue of over 28,000 people in more than 7,000 distress situations. In 2010 alone, the system provided information which was used to rescue 2,388 persons in 641 distress situations.

Most beacons are brightly colored and waterproof. EPIRBs and ELTs are larger, and would fit in a cube about 30 cm (12 in) on a side, and weigh 2 to 5 kg (4.4 to 11.0 lb). PLBs vary in size from cigarette-packet to paperback book and weigh 200 g to 1 kg (½ to 2½ lb). They can be purchased from marine suppliers, aircraft refitters, and (in Australia and the United States) hiking supply stores. The units have a useful life of 10 years, operate across a range of conditions −40 to 40 °C (−40 to 104 °F), and transmit for 24 to 48 hours. The cost of radiobeacons varies according to performance and specifications.