Defense Base Act — legislation that extends the Longshore and Harbor Workers' Compensation Act (LHWCA) to apply to certain categories of employees working overseas. The three general divisions of covered employees are (1) those working on military bases acquired from a foreign government after 1940, (2) employees of civilian contractors and subcontractors engaged in public work projects for the U.S. government outside the continental United States, and (3) individuals employed outside the continental United States by a U.S. employer whose purpose it is to provide welfare or other such services to the Armed Forces as approved by the secretary of defense.