The United States Department of the Navy (Navy) prepared this Environmental Impact Statement (EIS)/Overseas EIS (OEIS) in compliance with the National Environmental Policy Act (NEPA) of 1969 (42 United States Code §4321 et seq.); the Council on Environmental Quality Regulations for Implementing the Procedural Provisions of NEPA (Title 40 Code of Federal Regulations [C.F.R.] §§1500 et seq.); Navy Procedures for Implementing NEPA (32 C.F.R. §775); and Executive Order 12114, Environmental Effects Abroad of Major Federal Actions. The Navy identified its need to support and conduct current, emerging, and future training and testing activities in the Hawaii-Southern California Study Area, which is made up of air and sea space off Southern California, around the Hawaiian Islands, and the air and sea space connecting them. Three alternatives were analyzed in this EIS/OEIS: The No Action Alternative represents those training and testing activities as set forth in previously completed environmental planning documentation. Alternative 1 includes the training and testing activities addressed in the No Action Alternative, plus an adjustment to the Hawaii study area boundaries and proposed adjustments to types, location, and levels of training and testing activities. Alternative 2 includes all elements of Alternative 1 plus establishes new range capabilities, modifies existing capabilities, and adjusts the type and tempo of training and testing. In this EIS/OEIS, the Navy analyzed potential environmental impacts that result or could result from activities under the No Action Alternative, Alternative 1, and Alternative 2. The resources evaluated include sediments and water quality, air quality, marine habitats, marine mammals, sea turtles, seabirds, marine vegetation, marine invertebrates, fish, cultural resources, socioeconomic resources, and public health and safety.