The U.S. Navy operates three types of submarines- nuclear-powered ballistic missile submarines (SSBNs), nuclear-powered cruise missile and special operations forces (SOF) submarines (SSGNs), and nuclear-powered attack submarines (SSNs). This book provides background information and issues for Congress on the Virginia-class SSN program. The Navy's proposed FY2016 budget requests $5,340.1 million in procurement, advance procurement (AP), and Ecomic Order Quantity (EOQ) funding for the program. Decisions that Congress makes on procurement of Virginia-class boats could substantially affect U.S. Navy capabilities and funding requirements, and the U.S. shipbuilding industrial base. Furthermore, this book provides background information and potential oversight issues for Congress on the Ohio replacement program (ORP), a program to design and build a new class of 12 ballistic missile submarines (SSBNs) to replace the Navy's current force of 14 Ohio-class SSBNs. The Ohio replacement program is also kwn as the SSBN(X) program. The Navy wants to procure the first Ohio replacement boat in FY2021, with advance procurement (AP) funding starting in FY2017. The Navy has identified the Ohio replacement program as its top priority program.