This paper serves as an introduction to a symposium on the role that California oil and gas platforms serve as habitats for fishes and invertebrates. As of 2019, there are 27 platforms in state and federal waters off California, and the decommissioning of some of these platforms is imminent. Thus, consideration of whether to completely remove a platform or cut it off at some depth below the sea surface and retain the submerged portion as a reef is a decision that will occur in the near future. The objectives of the 10 papers in this dedicated issue of the Bulletin of Marine Science are to: (1) increase scientific understanding of the inter- and intrarelationships of fish and invertebrate populations at offshore oil and gas platforms and natural reefs within the Southern California Bight; (2) determine the extent of influence of platform assemblages on southern California and the Pacific coast populations of fishes and invertebrates; and (3) synthesize relevant reports, existing peer-reviewed literature, and new data analyses into a single peer-reviewed reference. This introductory paper contains a synopsis of all extant California platforms including information on: (1) the original operator, (2) the current operator of records, (3) the date the platform was installed, (4) the first production date, (5) the platform’s distance from shore [including whether it is state or outer continental shelf (OCS) waters], (6) the bottom depth of the platform, (7) the number of well slots, (8) the number of conductors, (9) what the platform produces (oil and/or gas), (10) the platform jacket dimensions [generally at the seafloor (bottom)], (11) the platform’s footprint, (12) the midwater surface area, (13) the total removal weight, (14) the platform location, (15) the shell mound size, (16) the shell mound volume, (17) the shell mound height, (18) the center of the shell mound location, and (19) the bottom slope. In addition, we present an overview of all previous research on the biology and ecology of California platform organisms.