The Social Security Act of 1935 is a law enacted by the 74th United States Congress and signed into law by U.S. President Franklin D. Roosevelt on August 14, 1935. The law created the Social Security program as well as insurance against unemployment. The law was part of Roosevelt's New Deal domestic program.

By 1930, the United States was one of the few industrialized countries without any national social security system. Amid the Great Depression, the physician Francis Townsend galvanized support behind a proposal to issue direct payments to older people. Responding to that movement, Roosevelt organized a committee led by Secretary of Labor Frances Perkins to develop a major social welfare program proposal. Roosevelt presented the plan in early 1935 and signed the Social Security Act into law on August 14, 1935. The Supreme Court upheld the act in two major cases decided in 1937.

The law established the Social Security program. The old-age program is offset by payroll taxes, and over the ensuing decades, it contributed to a dramatic decline in poverty among older people, and spending on Social Security became a significant part of the federal budget. The Social Security Act also established an unemployment insurance program administered by the states and the Aid to Dependent Children program, which provided aid to families headed by single mothers. The law was later amended by acts such as the Social Security Amendments of 1965, which established two major healthcare programs: Medicare and Medicaid.

Industrialization and the urbanization in the 20th century created many new social problems and transformed ideas of how society and the government should function together because of them. As industry expanded, cities grew quickly to keep up with demand for labor. Tenement houses were built quickly and poorly, cramming new migrants from farms and Southern and Eastern European immigrants into tight and unhealthy spaces. Work spaces were even more unsafe.

By the 1930s, the United States was one of the few modern industrial countries in which people faced the Depression without any national system of social security, though a handful of states had poorly-funded old-age insurance programs. The federal government had provided pensions to veterans in the aftermath of the Civil War and other wars, and some states had established voluntary old-age pension systems, but otherwise, the United States had little experience with social insurance programs. For most American workers, retirement during old age was not a realistic option. In the 1930s, the physician Francis Townsend galvanized support for his pension proposal, which called for the federal government to issue direct $200-a-month payments to the elderly. Roosevelt was attracted to the general thinking behind Townsend's plan because it would provide for those no longer capable of working, stimulate demand in the economy, and decrease the supply of labor. In 1934, the Dill-Connery bill for federal funding of state pensions programs, passed the House of Representatives and came near passage in the Senate that May. According to one study, ‘Roosevelt took ‘no open stand on the bill, but called supporters to the White House and persuaded them to delay passage until the administration prepared its own, "more comprehensive version.”’

A similar delay took place in relation to unemployment insurance. In February 1934, the Wagner-Lewis bill was introduced, which sought to establish a system of unemployment insurance. The Wagner-Lewis bill was favored by Roosevelt, although Republicans and more conservative Democrats strongly opposed it and (as noted by one study) “was not pushed by the administration with any real vigor. Nevertheless, many close observers believed that had Roosevelt taken a decided stand in favor of the bill it would have been passed by Congress. As with the Dill-Connery bill, the Wagner-Lewis bill failed to pass. According to friends of Roosevelt’s, “his only purpose was to have the problems studied more carefully and that he believed public sentiment was not yet sufficiently crystallized in favor of such a program.”

In 1934, Roosevelt charged the Committee on Economic Security, chaired by Secretary of Labor Frances Perkins, with developing an old-age pension program, an unemployment insurance system, and a national health care program. The proposal for a national health care system was dropped, but the committee developed an unemployment insurance program that would be largely administered by the states. The committee also developed an old-age plan; at Roosevelt's insistence, it would be funded by individual contributions from workers.

In January 1935, Roosevelt proposed the Social Security Act, which he presented as a more practical alternative to the Townsend Plan. After a series of congressional hearings, the Social Security Act became law in August 1935. During the congressional debate over Social Security, the program was expanded to provide payments to widows and dependents of Social Security recipients. Job categories that were not covered by the act included workers in agricultural labor, domestic service, government employees, and many teachers, nurses, hospital employees, librarians, and social workers. As a result,