Mark Edward Kelly (born February 21, 1964) is an American politician, former astronaut, and United States Navy captain who has served as the junior United States senator from Arizona since 2020. A member of the Democratic Party, he was elected in the special election held following the death of Senator John McCain, defeating incumbent Republican Martha McSally. Kelly flew combat missions during the Gulf War as a naval aviator before being selected as a NASA Space Shuttle pilot in 1996. He flew his first space mission in 2001 as pilot of STS-108, piloted STS-121 in 2006, and commanded STS-124 in 2008 and STS-134 in 2011, the final mission of Space Shuttle Endeavour. His identical twin, Scott Kelly, is also a retired astronaut; they are the only siblings to have both traveled into orbit.Kelly's wife, then-Arizona Congresswoman Gabby Giffords, was shot and nearly killed in an assassination attempt on January 8, 2011. Six people died in the Tucson shooting. After the Sandy Hook Elementary School shooting the following year, Giffords and Kelly founded the nonprofit Americans for Responsible Solutions, later renamed Giffords, which campaigns for gun control measures like universal background checks and red flag laws.Kelly announced his candidacy for Arizona's Class 3 U.S. Senate seat in the 2020 special election on February 12, 2019. He won the Democratic primary on August 4, 2020, and defeated incumbent Republican Martha McSally in the November 3, 2020, general election, becoming the first Democrat to win this seat since 1962. Kelly was sworn in on December 2, 2020. In 2022, he was elected to a full term in office, defeating Republican challenger Blake Masters. Kelly will become the senior senator from Arizona in January 2025, when Kyrsten Sinema leaves the Senate.