Giffords graduated from Tucson’s University High School. She is a former Girl Scout. She received a Bachelor of Arts degree in Sociology and Latin American History from Scripps College in California in 1993; and spent a year as a Fulbright Scholar in Chihuahua, Mexico. She returned to graduate school, earning a Master’s degree in Regional Planning from Cornell University in 1996. She focused her studies on Mexican-American relations.

Giffords worked as an associate for regional economic development at Price Waterhouse in New York City. In 1996, she became president and CEO of El Campo Tire Warehouses, a local chain of auto service centers founded by her grandfather. The business was sold to Goodyear Tire in 2000. At the time of the sale, she commented on the difficulties local businesses face when competing against large national firms.

Giffords switched her party affiliation from Republican to Democratic in 2000 and was elected to the Arizona House of Representatives from 2001 to 2003. She was elected to the Arizona Senate in the fall of 2002, and at the time was the youngest woman elected to that body. She took office in January 2003 and was re-elected in 2004. She resigned from the Arizona Senate on December 1, 2005, in preparation for her congressional campaign.

Since 2001, she has practiced Judaism exclusively and belongs to Congregation Chaverim, a Reform synagogue, in Tucson.

Her Republican opponent in the general election was Randy Graf, a conservative former state senator known for his enforcement-only position on immigration and illegal aliens. Graf had run against Jim Kolbe in the 2004 GOP primary and had announced his candidacy in 2006 before Kolbe announced his retirement. The Republican establishment was somewhat cool toward Graf, believing he might be too conservative for the district. The national GOP took the unusual step of endorsing one of the more moderate candidates in the primary. Graf won anyway, helped by a split in the Republican moderate vote between two candidates.

In early 2005, Giffords observed that “the 2004 election took its toll on our bipartisan coalition” and that as a result “a number of significant problems will receive far less attention than they deserve.” She highlighted among these, the lack of high-paying jobs or necessary infrastructure, rapid growth, and inward migration that threatened the environment and “strain[ed] […] education, health care, and transportation,” and unresolved problems such as Students First; Arnold v. Sarn; repayments due under Ladewig v. Arizona; the No Child Left Behind mandate; low educational achievement; health care costs; and the demands of the Arizona Health Care Cost Containment System. She noted that Arizona was not alone in facing such challenges.

Giffords is a former member of the Arizona regional board of the Anti-Defamation League. After Hurricane Katrina struck in August 2005, Giffords spent time as a volunteer in Houston, Texas, in relief efforts for hurricane victims. She wrote about her experience in the Tucson Citizen.

Giffords launched her first candidacy for the U.S. Congress on January 24, 2006. The campaign received national attention early on as a likely pick-up for the Democratic Party. Prominent Democrats, including Tom Daschle, Robert Reich, Janet Napolitano, and Bill Clinton, endorsed Giffords. EMILY’s List endorsed Giffords early in the campaign cycle. The Sierra Club and the Arizona Education Association also endorsed her. On September 12, 2006, Giffords won her party’s nomination in the primary election.

Not long after the primary, Congressional Quarterly changed its rating of the race to “Leans Democrat”. By late September, the national GOP had pulled most of its funding, effectively conceding the seat to Giffords. Giffords won the race on November 7, 2006, with 54 percent of the vote. Graf received 42 percent. The rest of the vote went to minor candidates. Giffords’s victory was portrayed as evidence that Americans are accepting towards comprehensive immigration reform. She was the first woman with a Jewish father elected to Congress from Arizona.

Giffords is an avid reader, and was featured on NPR’s Weekend Edition on July 9, 2006, talking about her love of books. She was periodically interviewed in 2007 together with Illinois Republican Peter Roskam on NPR’s All Things Considered. The series focused on their experiences as freshman members of the 110th Congress.

Following the November 2006 election, Giffords was sworn in as a congresswoman on January 3, 2007. She was the third woman in Arizona’s history to be elected to serve in the U.S. Congress. In her inaugural speech on the floor of the House of Representatives, Giffords advocated a comprehensive immigration reform package, including modern technology to secure the border, more border patrol agents, tough employer sanctions for businesses that knowingly hire illegal immigrants, and a guest-worker program. In her first month in office, Giffords voted in favor of increased federal funding for embryonic stem-cell research; raising the minimum wage; endorsing the 9/11 Commission recommendations; new rules for the House of Representatives targeting ethical issues; and the repeal of $14 billion of subsidies to big oil companies, in favor of renewable energy subsidies and the founding of the Strategic Renewable Energy Reserve.

During the 2007 session of Congress, Giffords introduced a bill (H.R. 1441) that forbids the sale of F-14 aircraft parts on the open market to prevent them from being acquired by Iran. Giffords advocated for a national day of recognition for cowboys as one of her first actions. She voted for the contentious May 2007 Iraq Emergency Supplemental Spending bill, saying, “I cannot, in good conscience, allow the military to run out of money while American servicemen and women are being attacked every day”. She has also been a Girl Scout supporter for many years. On April 21, 2007, Giffords hosted her third “Congress on Your Corner” in Tucson, Arizona, and kicked things off by speaking to the Girl Scouts of Southern Arizona, Sahuaro Council.

Giffords married U.S. Navy Captain, NASA astronaut and US Senator-elect Mark Kelly on November 10, 2007. Kelly was the Space Shuttle’s pilot on the STS-108 and STS-121 missions, and was the commander of STS-124 and STS-134.

In September 2007, she published a report titled: The Community Solar Energy Initiative, Solar Energy in Southern Arizona, observing that Arizona has enough sunshine to power the entire United States. It reviews current energy usage and discusses how to increase the production of solar electricity. On August 1, 2008, she wrote to congressional leaders regarding tax credits that were set to expire, saying that failure to extend the scheme would be extremely harmful to the renewable energy industry “just as it is beginning to take off.”

In 2008, Giffords was elected to a second term. Republican Tim Bee, a childhood classmate and former colleague in the Arizona State Senate, ran against her. Bee was the President of the Arizona State Senate and considered a strong challenger in this race. Despite native son John McCain’s running as the Republican presidential candidate, Giffords was reelected with 56.20 percent of the vote to Bee’s 41.45 percent.

In 2008, Giffords introduced legislation that would have increased the cap on the H-1B visa from 65,000 per year to 130,000 per year. If that were not sufficient, according to her legislation, the cap would have been increased to 180,000 per year. The bill would have allowed, at most, 50% of employees at any given company with at least 50 employees to be H-1B guest workers. Giffords said the bill would help high-tech companies in southern Arizona, some of which rely on H-1B employees. However, Giffords’s bill was never voted on by the House of Representatives.

In 2008, before being shot, Giffords opposed Washington D.C. prohibitions on possession of handguns in the home and having usable firearms there, signing an amicus brief with the U.S. Supreme Court to support its overturn.

On November 5, 2010, Giffords was declared the victor after a close race against Republican Jesse Kelly. Kelly, an Iraq War veteran (and not related to Mark Kelly), was listed as a top-ten Tea Party candidate to watch by Politico, and described by The Arizona Republic as highly conservative even compared to Sarah Palin. Giffords had been targeted for defeat by Sarah Palin’s political action committee, SarahPAC.

On August 31, 2010, Giffords praised the arrival of National Guard troops on the border: “Arizonans have waited a long time for the deployment of the National Guard in our state. Their arrival represents a renewed national commitment to protecting our border communities from drug cartels and smugglers.”

Giffords participated in the reading of the United States Constitution on the floor of the House of Representatives on January 6, 2011; she read the First Amendment.

On January 8, 2011, Giffords was shot in the head outside a Safeway grocery store in Casas Adobes, Arizona, a suburban area northwest of Tucson, during her first “Congress on Your Corner” (a public opportunity for constituents to speak directly with their representatives) gathering of the year. A man ran up to the crowd and began firing a 9mm pistol with a 33-round magazine, hitting 19 people, and killing six, among them federal judge John Roll and a 9-year-old child, Christina-Taylor Green. A 20th person was injured at the scene, but not by gunfire.

On March 12, 2011, Giffords’s husband informed her that six other people had been killed in the attack on her, but he did not identify who they were until months later. In late April, Giffords’s doctors reported that her physical, cognitive, and language production abilities had improved significantly, placing her in the top 5 percent of patients recovering from similar injuries. She was walking under supervision with perfect control of her left arm and leg, and able to write with her left hand. She was able to read and understand, and spoke in short phrases. With longer efforts, she was able to produce more complex sentences.

After continuing her rehabilitation therapy in Houston, Giffords returned to KSC for her husband’s launch on May 16, 2011. Kelly wore his wife’s wedding ring into space, which she had exchanged for his.

Giffords underwent cranioplasty surgery on May 18, 2011, to replace the part of her skull that had been removed in January to permit her brain to swell after the gunshot to her head. Surgeons replaced the bone with a piece of molded hard plastic, fixed with tiny screws; they expected that her skull would eventually fuse with the plastic’s porous material. At that point, Giffords no longer needed to wear the helmet that she had been wearing to protect her brain from further injury. On June 9, 2011, Giffords’s aide Pia Carusone announced that while Giffords’s comprehension appeared to be “close to normal, if not normal”, she was not yet using complete sentences. On June 12, two photos of Giffords taken on May 17 were released, the first since the shooting. On June 15, Giffords was released from the hospital to return home, where she continued speech, music, physical and occupational therapy. Having learnt the French horn as a child she returned to the instrument as part of her music therapy and in August 2020 spoke about this experience in a speech endorsing Joe Biden’s presidential bid.

On August 1, 2011, she made her first public appearance on the House floor to vote in favor of raising the debt limit ceiling. She was met with a standing ovation and accolades from her fellow members of Congress. A Giffords spokesman, Mark Kimble, stated in August 2011 that the congresswoman was walking without a cane and was writing left-handed, as she did not have full use of her right side. On October 6, Giffords traveled to Washington for her husband’s retirement ceremony, where she presented him with the Distinguished Flying Cross medal. She returned to her husband’s Texas home. On October 25, 2011, she travelled to Asheville, North Carolina, for intensive rehabilitation treatments, ending November 4. In Kelly’s memoir, Gabby: A Story of Courage and Hope, released in November 2011, he reported that Giffords would return to Congress. She continues to struggle with language and has lost fifty percent of her vision in both eyes.

A joint memoir by Giffords and Kelly, Gabby: A Story of Courage and Hope, with co-author Jeffrey Zaslow, was published on November 15, 2011. Giffords and Kelly were interviewed by ABC’s Diane Sawyer in their first joint interview since the shooting, which aired on a special edition of 20/20 on November 14, 2011, in conjunction with the book’s publication.

In August 2011, she voted in favor of raising the debt ceiling.

On January 22, 2012, Giffords announced in a video statement that she intended to resign her seat so that she could continue to focus on her recovery. She attended President Obama’s 2012 State of the Union Address on January 24, and formally submitted her resignation on January 25. Appearing on the floor of the House, after the last bill she sponsored was brought to a vote and unanimously passed, Giffords was lauded by members of Congress and the majority and minority leaders who spoke in tribute to her strength and accomplishment in an unusual farewell ceremony. Her letter of resignation was read on her behalf by her close friend and fellow Democratic representative, Debbie Wasserman Schultz.

On September 6, 2012, Giffords led the Pledge of Allegiance at that evening’s meeting of the Democratic National Convention. In January 2013, Giffords still had difficulty speaking and walking, and her right arm was paralyzed. She continued to undergo speech and physical therapy.

It was announced by Secretary of the Navy Ray Mabus, on February 10, 2012, that the next U.S. Navy littoral combat ship would be named USS Gabrielle Giffords (LCS-10). Rep. Giffords, still recovering from injuries sustained in the 2011 assassination attempt, attended the ship’s keel-laying ceremony and etched her initials into a plate welded into the ship.

In January 2013, Giffords and her husband Mark Kelly started a political action committee called Americans for Responsible Solutions whose mission is to promote gun-control legislation with elected officials and the general public. The couple supports “keeping guns out of the hands of dangerous people like criminals, terrorists, and the mentally ill”.

Giffords was a surprise witness at a Senate Judiciary Committee hearing on gun violence on January 30, 2013. In a halting voice, she called for Congress to pass tougher laws on guns, saying “too many children are dying.” Giffords is right-handed; her speech therapist had to write out her statement for her since her right arm was paralyzed in the shooting.

On January 8, 2014, Giffords marked the third anniversary of the shooting by going skydiving. Giffords said on an interview with the Today show, “Oh, wonderful sky. Gorgeous mountain. Blue skies. I like a lot. A lot of fun. Peaceful, so peaceful.”

USS Gabrielle Giffords was christened at the Austal USA shipyard in Mobile, Alabama, on June 13, 2015. Rep. Giffords attended the christening ceremony, along with Second Lady of the United States Jill Biden, who served as the ship’s sponsor. The ship was commissioned on June 12, 2017, at Port of Galveston, Texas.

After her shooting, Giffords became an advocate for anti-gun-violence causes. In 2017, after the Las Vegas shooting that killed 58 and injured 546, she implored lawmakers to take action, saying she “knows the horror of gun violence all too well”.

In 2020 she spoke on the third night of the 2020 Democratic National Convention, urging action on gun control. She worked with a speech therapist for months in preparation for the speech, and also performed “America” on the French horn, an instrument she had played as a teen, as a symbol of her recovery.