Mark Edward Kelly is the son of Richard and Patricia (née McAvoy) Kelly, two retired police officers. He is of Irish descent. He was born on February 21, 1964, in Orange, New Jersey, and raised in West Orange, New Jersey. Kelly graduated from Mountain High School in 1982. He received a Bachelor of Science in marine engineering and nautical science from the United States Merchant Marine Academy, graduating with highest honors in 1986. In 1994, he received a Master of Science in aeronautical engineering from the U.S. Naval Postgraduate School.

In December 1987, Kelly became a naval aviator and received initial training on the A-6E Intruder attack aircraft. He was then assigned to Attack Squadron 115 (VA-115) in Atsugi, Japan, and made two deployments to the Persian Gulf on the aircraft carrier USS Midway, flying 39 combat missions in Operation Desert Storm. After receiving his master’s degree, Kelly attended the U.S. Naval Test Pilot School from 1993 to 1994. He has logged more than 5,000 hours in more than 50 different aircraft and has over 375 carrier landings.

Kelly married Amelia Victoria Babis on January 7, 1989. They divorced in 2004. They have two daughters, Claudia and Claire Kelly.

NASA selected both Mark and Scott Kelly to be Space Shuttle pilots in 1996. They joined the NASA Astronaut Corps in August of that year. Mark Kelly has logged over 54 days in space. During his 2006 flight on Space Shuttle Discovery, the second mission after the loss of Space Shuttle Columbia, Kelly discussed the risks of flying the Space Shuttle:

Kelly’s first trip into space was as pilot of STS-108. After several delays, Endeavour lifted off on December 5, 2001, on the final Shuttle mission of 2001.

In July 2006, Kelly piloted STS-121 Discovery, the second “Return to Flight” mission following the loss of Columbia in February 2003. Because of weather delays, STS-121 became the first shuttle mission to launch on the Fourth of July.

Kelly married U.S. Representative Gabby Giffords of Tucson, Arizona, on November 10, 2007, in a ceremony presided over by Rabbi Stephanie Aaron, and attended by his STS-124 shuttle crew and former Secretary of Labor Robert Reich. Reich toasted: “To a bride who moves at a velocity that exceeds that of anyone else in Washington, and a groom who moves at a velocity that exceeds 17,000 miles per hour.” The couple met on a 2003 trip to China as part of a trade mission sponsored by the National Committee on U.S.–China Relations.

Most of the mission’s delays were caused by external tank issues on STS-133 Discovery. When Scott Kelly went to the ISS on October 7, 2010, STS-134 was scheduled to go to the station during his mission. The potential rendezvous in space of the Kelly brothers would have been a first meeting of blood relatives in space. The delay of STS-134’s launch ended that possibility.

On June 21, 2011, Kelly announced his retirement from the U.S. Navy and NASA, effective October 1, 2011. His retirement was announced on his Facebook page, where he wrote, “Words cannot convey my deep gratitude for the opportunities I have been given to serve our great nation. From the day I entered the United States Merchant Marine Academy in the summer of 1982 to the moment I landed the Space Shuttle Endeavour three weeks ago, it has been my privilege to advance the ideals that define the United States of America.”

On April 29, 2011, the first launch attempt of STS-134 was scrubbed. Giffords traveled to Florida on her first trip since moving from Tucson to Houston in January after an attempted assassination. Her appearance at Kennedy Space Center gave the launch a high profile, “one of the most anticipated in years,” according to The New York Times. President Obama visited the Kennedy Space Center on April 29 on a trip with the original intention of watching the Endeavour launch.

After his wife’s shooting, Mark Kelly’s status was unclear, but NASA announced on February 4, 2011, that he would remain commander of the mission. The remarkable progress his wife was making in her recovery helped Kelly decide to return to training. Peggy Whitson, chief of the NASA Astronaut Office at the time, said, “we are confident in his ability to successfully lead this mission, and I know I speak for all of NASA in saying ‘welcome back.'”

At 4 pm PDT on May 22, 2011, the European Space Agency and Italian Space Agency arranged for a call to Endeavour by Pope Benedict XVI. During his call—prompted by the discovery of a gash in the Shuttle’s fuselage—Benedict extended his blessing to Giffords, who had undergone skull surgery earlier in the week. The event marked the first time a pope spoke to astronauts during a mission.

On June 24, 2011, a recorded message by Kelly from the ISS wished his wife love using song lyrics from David Bowie’s “Space Oddity” and introduced U2’s song “Beautiful Day” on the first night of the Glastonbury festival in England. A similar message from Kelly aboard the ISS was played during U2’s 360° Tour concert stop at various locations. It said: “I’m looking forward to coming home. Tell my wife I love her very much. She knows.”

On June 21, 2011, Kelly announced that he would leave NASA’s astronaut corps and the U.S. Navy effective October 1. He cited Giffords’s needs during her recovery as a reason for his retirement.

In 2011, Kelly and Giffords coauthored Gabby: A Story of Courage, Love and Resilience. The book provides biographical information on the couple and describes in detail the assassination attempt on Giffords and her initial recovery. Written in Kelly’s voice, it includes a short note by Giffords at the end.

Giffords was shot in an assassination attempt on January 8, 2011, putting Kelly in the national spotlight. On February 4, Kelly described the previous month as the hardest time of his life and expressed his gratitude for the enormous outpouring of support, good wishes and prayers for his wife. He said that he believed people’s prayers for her helped.

A memorial service for those killed in the assassination attempt was held on January 12, 2011, at the University of Arizona. President Barack Obama flew to Tucson to speak at the memorial. Kelly sat between First Lady Michelle Obama and Secretary of Homeland Security Janet Napolitano, the previous governor of Arizona. At the end of the service, Obama consoled and embraced him, after which Kelly returned to the hospital to be with his wife.

Kelly spoke on February 3, 2011, at the National Prayer Breakfast in Washington, DC. His remarks closed the event, where Obama also spoke. Kelly said the attack on his wife brought him closer to God and gave him a newfound awareness regarding prayer. He said that before the attack, “I thought the world just spins and the clock just ticks and things happen for no particular reason”, but that, in Tucson, as he found himself wandering in makeshift memorials and shrines filled with Bibles and angels, “You pray where you are. You pray when God is there in your heart.” Kelly offered the final prayer of the morning. The prayer was from Rabbi Stephanie Aaron, who married Kelly and Giffords, and who said the same words over Giffords on the night of the shooting:

In 2011, Kelly said he believed there was a chance to change a political environment he believed was too vitriolic. He hoped that the tragedy would be an opportunity to improve the tone of the national dialogue and cool down the rhetoric. In response to a question on February 4, 2011, about civility in politics, Kelly said, “I haven’t spent a lot of time following that, but I think that with something that was so horrible and so negative, and the fact that six people lost their lives including a nine-year-old girl, a federal judge, Gabby’s staff member Gabe—who was like a younger brother to her—it’s really, really a sad situation. I am hopeful that something positive can come out of it. I think that will happen, so those are good things.”

On March 28, 2012, SpaceX announced that Kelly would be part of an independent safety advisory panel composed of leading human spaceflight safety experts.

In January 2013, Kelly and Giffords started a political action committee, Americans for Responsible Solutions. The organization’s mission is to promote solutions to gun violence with elected officials and the general public. The couple say it supports the Second Amendment while promoting responsible gun ownership and “keeping guns out of the hands of dangerous people like criminals, terrorists, and the mentally ill.” The group claims that “current gun laws allow private sellers to sell guns without a background check, creating a loophole that provides criminals and the mentally ill easy access to guns”. On March 31, 2013, Kelly said, “any bill that does not include a universal background check is a mistake. It’s the most common-sense thing we can do to prevent criminals and the mentally ill from having access to weapons.” In 2016, Americans for Responsible Solutions joined the Law Center to Prevent Gun Violence and launched a joint organization known as “Giffords”.

In 2014, Giffords and Kelly coauthored Enough: Our Fight to Keep America Safe from Gun Violence.

In 2015, Kelly and Martha Freeman cowrote Astrotwins: Project Blastoff, a fictional story about twins Scott and Mark who build a space capsule in their grandfather’s backyard and try to send the first kid into orbit. Kelly dedicated this book to Scott Kelly. The sequel, Astrotwins—Project Rescue, was published in 2016.

On February 12, 2019, Kelly announced that he would run as a Democrat in the 2020 United States Senate special election in Arizona. Kelly looked to unseat incumbent Republican Martha McSally, a fellow veteran who was appointed to the position shortly after losing a Senate election to Democrat Kyrsten Sinema. The seat was vacated upon the resignation of a previous Republican gubernatorial appointee, Jon Kyl.

The Associated Press called the race for Kelly on November 4. As the election was a special election, Kelly will take office during the 116th Congress on November 30, unlike other senators and representatives elected in 2020, who will take office at the opening of the 117th Congress on January 3, 2021. Kelly’s term ends in 2023, after which his seat will be occupied by the winner of the 2022 election, in which he is likely to run.

In his 2020 bid for U.S. Senate, Kelly pledged to refuse donations from corporate political action committees (PACs). He did not entirely eschew corporate money, headlining a Washington, D.C., fundraiser hosted by lobbyists and earning money on the speakers circuit from corporate-aligned groups.