John Wright Hickenlooper Jr. (born February 7, 1952) is an American politician serving as the junior United States senator from Colorado since 2021. A member of the Democratic Party, he served as the 42nd governor of Colorado from 2011 to 2019 and as the 43rd mayor of Denver from 2003 to 2011. He was a geologist and businessman before entering politics.

Born in Narberth, Pennsylvania, Hickenlooper is a graduate of Wesleyan University. After a career as a petroleum geologist, in 1988 he co-founded the Wynkoop Brewing Company, one of the first brewpubs in the U.S. Hickenlooper was elected the 43rd mayor of Denver in 2003, serving two terms. In 2005, TIME named him one of America's five best big-city mayors. After incumbent governor Bill Ritter said that he would not seek reelection, Hickenlooper announced his intention to run for the Democratic nomination in January 2010. He won an uncontested primary and faced Constitution Party nominee Tom Tancredo and Republican Party nominee Dan Maes in the general election. Hickenlooper won with 51% of the vote and was reelected in 2014, defeating Republican Bob Beauprez.

As governor, he introduced universal background checks and banned high-capacity magazines in the wake of the 2012 Aurora, Colorado shooting. He expanded Medicaid under the provisions of the Affordable Care Act, halving the rate of uninsured people in the state. Having initially opposed marijuana legalization, he has gradually come to support it.

He sought the Democratic nomination for U.S. president in 2019 but dropped out before primaries were held. He subsequently ran for the U.S. Senate, winning the Democratic nomination and the general election, defeating incumbent Republican Cory Gardner. At 68, Hickenlooper became the oldest first-term senator to represent Colorado and the only Quaker member of Congress.