King v. Smith, 392 U.S. 309 (1968), was a unanimous decision in which the Supreme Court of the United States held that Aid to Families with Dependent Children (AFDC) could not be withheld because of the presence of a "substitute father" who visited a family on weekends.

The issue before the US Supreme Court involved how the states could determine how to implement a federal program.

Shapiro v. Thompson, King v. Smith and Goldberg v. Kelly were a set of successful Supreme Court cases that dealt with Welfare, specifically referred to as a part of 'The Welfare Cases'.

[1] Mrs. Sylvester Smith was a Dallas County, Alabama resident who had four children, without a biological father providing support.

Williams, who visited on weekends, was counted as a "substitute father", thus disqualifying the family for aid according to Alabama Law.