The American Shipyard Investment Act of 2026 creates a federal tax credit to encourage investment in U.S. shipyard facilities and related manufacturing. Companies that construct, repair, or maintain commercial or military vessels, or manufacture critical vessel components and equipment, can claim a tax credit equal to 25 percent of their qualified investment in these facilities, with the credit increasing to 35 percent for facilities located in economically distressed areas. The bill affects shipbuilders, vessel manufacturers, and equipment suppliers across the country by reducing their federal tax liability on investments in qualifying shipyard infrastructure. The tax credit is available for property placed in service after the bill's introduction through December 31, 2033, providing an eight-year window for companies to take advantage of the incentive. This legislation aims to strengthen domestic shipbuilding capacity as part of U.S. national defense and economic security.