The Burst Alert Telescope (BAT) is one of three instruments on the Swift spacecraft designed to study gamma-ray bursts (GRBs). The BAT detects GRBs within 20 seconds of the event and localizes the burst direction to an accuracy of 1-4 arcmin. It then autonomously slews the spacecraft to point the X-ray Telescope (XRT) and Ultraviolet/Optical Telescope (UVOT) at the burst location for follow-up observations. The BAT is a wide-field, coded-aperture instrument with a CdZnTe detector plane and a 1.4 sr (half-coded) field of view. It operates over the 15-150 keV energy range with a sensitivity of ~10^-8 erg s^-1 cm^-2 and is expected to detect over 100 GRBs per year. The BAT also performs an all-sky hard x-ray survey with a sensitivity of ~2 mCrab and serves as a hard x-ray transient monitor. The BAT's design includes a detector plane of 32,768 CdZnTe elements and a coded-aperture mask of ~52,000 lead tiles. The BAT's performance is enhanced by its ability to handle large FOV and its use of coded-aperture techniques. The BAT's onboard processing system includes an Image Processor that performs burst detection, location, and data processing. The BAT's operations include two modes: scan-survey mode and burst mode. The BAT's burst detection algorithm identifies excess count rates in the detector plane and uses an FFT-based algorithm to create an image of the sky. The BAT's burst location is determined with an accuracy of 1-4 arcmin. The BAT's hard x-ray survey provides a sensitivity of ~0.2 mCrab in the 15-100 keV band for 3 years. The BAT's data is transmitted to the ground via the TDRSS system and distributed to the global community through the GCN system. The BAT's design and operations are critical to the Swift mission's ability to study GRBs and other hard x-ray transients.The Burst Alert Telescope (BAT) is one of three instruments on the Swift spacecraft designed to study gamma-ray bursts (GRBs). The BAT detects GRBs within 20 seconds of the event and localizes the burst direction to an accuracy of 1-4 arcmin. It then autonomously slews the spacecraft to point the X-ray Telescope (XRT) and Ultraviolet/Optical Telescope (UVOT) at the burst location for follow-up observations. The BAT is a wide-field, coded-aperture instrument with a CdZnTe detector plane and a 1.4 sr (half-coded) field of view. It operates over the 15-150 keV energy range with a sensitivity of ~10^-8 erg s^-1 cm^-2 and is expected to detect over 100 GRBs per year. The BAT also performs an all-sky hard x-ray survey with a sensitivity of ~2 mCrab and serves as a hard x-ray transient monitor. The BAT's design includes a detector plane of 32,768 CdZnTe elements and a coded-aperture mask of ~52,000 lead tiles. The BAT's performance is enhanced by its ability to handle large FOV and its use of coded-aperture techniques. The BAT's onboard processing system includes an Image Processor that performs burst detection, location, and data processing. The BAT's operations include two modes: scan-survey mode and burst mode. The BAT's burst detection algorithm identifies excess count rates in the detector plane and uses an FFT-based algorithm to create an image of the sky. The BAT's burst location is determined with an accuracy of 1-4 arcmin. The BAT's hard x-ray survey provides a sensitivity of ~0.2 mCrab in the 15-100 keV band for 3 years. The BAT's data is transmitted to the ground via the TDRSS system and distributed to the global community through the GCN system. The BAT's design and operations are critical to the Swift mission's ability to study GRBs and other hard x-ray transients.