The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The project completed commissioning in summer 2009, and continued until December 2012. It has since been succeeded by the Intermediate Palomar Transient Factory (iPTF), which itself transitioned to the Zwicky Transient Facility in 2017/18. All three surveys are registered at the MPC under the same observatory code for their astrometric observations. Description The fully automated system included an automated realtime data reduction pipeline, a dedicated photometric follow-up telescope, and a full archive of all detected astronomical sources. The survey was performed with a 12K × 8K, 7.8 square degree CCD array camera re-engineered for the 1.2-meter Samuel Oschin Telescope at Palomar Observatory. The survey camera achieved first light on 13 December 2008. PTF was a collaboration of Caltech, LBNL, Infrared Processing and Analysis Center, Berkeley, LCOGT, Oxford, Columbia and the Weizmann Institute. The project was led by Shrinivas Kulkarni at Caltech. As of 2018, he leads the Zwicky Transient Facility. Image Subtraction for near-realtime transient detection was performed at LBNL; efforts to continue to observe interesting targets were coordinated at Caltech, and the data was processed and archived for later retrieval at the Infrared Processing and Analysis Center (IPAC). Photometric and spectroscopic followup of detected objects was undertaken by the automated Palomar 1.5-meter telescope and other facilities provided by consortium members. Time-variability studies were undertaken using the photometric/astrometric pipeline implemented at the Infrared Processing and Analysis Center (IPAC). Studies included compact binaries (AM CVn stars), RR Lyrae, cataclysmic variables, and active galactic nuclei (AGN), and lightcurves of small Solar System bodies. Scientific goals PTF covered a wide range of science aspects, including supernovae, novae, cataclysmic variables, Luminous red novae, tidal disruption flares, compact binaries (AM CVn star), active galactic nuclei, transiting Extrasolar planets, RR Lyrae variable stars, microlensing events, and small Solar System bodies of the Solar System. PTF filled the gaps in the knowledge of the optical transient phase space, extended the understanding of known source classes, and provided the first detections or constraints on predicted, but not yet discovered, event populations. Projects The efforts being undertaken during the five-year project include: a 5-day cadence supernova search an exotic transient search with cadences between 90 seconds and 1 day. a half-sky survey in the H-alpha