Claire Conner McCaskill (born July 24, 1953) is an American Democratic politician, currently the junior United States Senator from the state of Missouri and former State Auditor of Missouri. She defeated Republican Senator Jim Talent in 2006 by a margin of 50% to 47%. She is the first female senator from Missouri elected in her own right. She was cited by the New York Times to be among the seventeen women most likely to become the first female President of the United States. She will become the state's senior senator upon the retirement of Missouri's senior U.S. Senator, Kit Bond, in 2011.

McCaskill was born in Rolla, Missouri. McCaskill's father, William Y. McCaskill, served as a state Insurance Commissioner during the administration of Governor Warren E. Hearnes. Her mother Betty Anne was the first woman elected to the City Council of Columbia, Missouri. Interestingly, Betty Anne McCaskill lost a race for a seat in the state House of Representatives to Leroy Blunt, Governor Matt Blunt's grandfather. McCaskill spent her early childhood in the small Missouri town of Houston, later moving to Lebanon, and eventually Columbia. McCaskill attended David H. Hickman High School in Columbia, where she was a cheerleader and Pep Club president and was elected homecoming queen. While attending the University of Missouri, McCaskill joined Kappa Alpha Theta sorority, graduating in 1975 with a B.A. in political science. She received her Juris Doctor (J.D.) from The University of Missouri Law School in 1978.

Except for three years spent in private practice as an attorney at the firm of a leading Kansas City trial lawyer (1989 to 1991), McCaskill has worked in the public sector continuously since graduating from law school in 1978. Claire, following her graduation from law school, spent one year as a law clerk on the Missouri Court of Appeals for the Western District, which sits in Kansas City. Thereafter, McCaskill joined the Jackson County prosecutor's office where she specialized in arson cases. In 1982, McCaskill was elected to represent the Brookside neighborhood of Kansas City in the Missouri House of Representatives, where she became the first female attorney to serve in that body in approximately 40 years. During her time in the House, McCaskill became the first Missouri state lawmaker to give birth while in office. McCaskill left the state House to contemplate running for Jackson County Prosecutor in 1988, but did not pursue the position when fellow Democrat and incumbent Prosecutor Albert Riederer decided to seek another term. In 1990, McCaskill was elected to the Jackson County Legislature (the equivalent of a county commission or county council). In 1991, McCaskill made a bold announcement when she expressed her intention to run for County Prosecutor. The announcement was significant in that the elected Democratic Prosecutor Riederer had not announced that he wasn't going to seek re-election. McCaskill then went on to an impressive victory in capturing the Jackson County Prosecutor's Office in 1992.