A comprehensive map of Quaternary faults has been generated for offshore of California. The Quaternary fault map includes mapped geometries and attribute information for offshore fault systems located in California State and Federal waters. The polyline shapefile has been compiled from previously published mapping where relatively dense, high-resolution marine geophysical data exist. The data are also available in kml format and are accompanied by a pdf containing citations for the compiled source data. In the last decade, a number of new marine geophysical datasets collected by the U.S. Geological Survey (USGS), the Ocean Exploration Trust, and other organizations has led to substantially improved high-resolution mapping of the seafloor in areas including California's mainland State waters and the southern California continental borderland. Data include comprehensive multibeam bathymetry, seismic-reflection, and marine magnetic data in numerous offshore areas. Most of these data have been processed, merged, and released by the USGS in maps, data releases, and journal publications in support of the California Seafloor Mapping Program and the U.S. West Coast and Alaska Marine Geohazards Project. Improved data coverage has allowed researchers to better map offshore faults in areas previously unmapped or covered only by low-resolution data. Additionally, subsurface imaging and seafloor sampling has led to better understanding of fault kinematics and recency of deformation, which are critical for accurately assessing California's seismic and coastal hazards.