William Hubbs Rehnquist (October 1, 1924 – September 3, 2005) was an American lawyer, jurist, and political figure who served as an Associate Justice on the Supreme Court of the United States and later as the 16th Chief Justice of the United States. Considered a conservative, Rehnquist favored a conception of federalism that emphasized the Tenth Amendment's reservation of powers to the states. Under this view of federalism, the Supreme Court of the United States, for the first time since the 1930s, struck down an Act of Congress as exceeding federal power under the Commerce Clause.
Rehnquist presided as Chief Justice for nearly 19 years, making him the fourth-longest-serving Chief Justice after John Marshall, Roger Taney, and Melville Fuller, and the longest-serving Chief Justice who had previously served as an Associate Justice. The last 11 years of Rehnquist's term as Chief Justice (1994–2005) marked the second-longest tenure of a single unchanging roster of the Supreme Court.
Rehnquist was born William Donald Rehnquist in Milwaukee, Wisconsin, on October 1, 1924. He grew up in the suburb of Shorewood. His father, William Benjamin Rehnquist, was a paper salesman; his mother, Margery Peck Rehnquist, was a translator and homemaker. Rehnquist changed his middle name to Hubbs, a family name, because a numerologist told his mother he would be successful with a middle initial of H. His paternal grandparents emigrated from Sweden.