Acoustic telemetry involves the use of sound to convey information relating to the presence of an animal as it moves from one location to another in the aquatic environment. In the context of shark research, this most commonly reects using acoustic transmitters and receivers to track movement of individuals. Originally, acoustic transmitters simply emitted a pulse that could be detected by a receiving device; researchers followed the sound using a directional hydrophone as the shark swam through the environment and recorded positions every few minutes to represent the movement track of an individual (Holland et al., 1992; Morrissey and Gruber, 1993). As technology developed, information was encoded into acoustic signals by using a series of pings that could be decoded by the receiver. This led to the capacity to provide unique identication codes for an individual tag, which allowed simultaneous tracking of multiple individuals. By combining coded transmitters with data-logging acoustic receivers that could be moored in study sites for long periods, the need for animals to be actively followed was removed. This revolutionized the eld of acoustic telemetry by allowing researchers to establish arrays of receivers to detect and track sharks automatically (Heupel et al., 2006). Sensors are also being developed and integrated with transmitters to provide information on the environments that tagged sharks encounter (e.g., depth, temperature) and their behavioral state (e.g., acceleration). Similarly, advances in receiver systems, collaborations, and modes to access stored data provide new ways to examine shark behavior and distribution at broad scales. In this chapter, we discuss the application of acoustic telemetry to track sharks, advances to the technology over time, and the challenges and opportunities this technology has provided to shark research.