Jared Lee Loughner (/ˈlɒfnər/; born September 10, 1988) is an American mass murderer who pled guilty to 19 charges of murder and attempted murder in connection with the January 8, 2011 Tucson shooting, in which he shot and severely injured U.S. Representative Gabrielle Giffords, his target, and killed six people, including Chief U.S. District Court Judge John Roll, as well as a nine-year-old bystander, Christina-Taylor Green. Loughner shot and injured a total of 13 people, while one man was injured while subduing him.

Records show that Loughner was registered as an Independent and voted in 2006 and 2008, but not in 2010.

According to a former friend, Bryce Tierney, Loughner had expressed a longstanding dislike for Gabrielle Giffords. Tierney recalled that Loughner had often said that women should not hold positions of power. He repeatedly derided Giffords as a "fake". This belief intensified after he attended her August 25, 2007 event when she did not, in his view, sufficiently answer his question: "What is government if words have no meaning?" Loughner kept Giffords' form letter, which thanked him for attending the 2007 event, in the same box as an envelope which was scrawled with phrases like "die bitch" and "assassination plans have been made". Zane Gutierrez, a friend, later told The New York Times that Loughner's anger would also "well up at the sight of President George W. Bush, or in discussing what he considered to be the nefarious designs of government."

Zach Osler, a high-school classmate of Loughner's and his closest friend, indicated that Loughner's life began to unravel after his high-school girlfriend broke up with him. He began to abuse alcohol and other drugs, including cannabis (marijuana), cocaine, psychedelic mushrooms, LSD, and Salvia divinorum (a hallucinogen legal in Arizona). After struggling with drugs for more than two years, Loughner gave up alcohol, tobacco, and recreational drugs in late 2008 and has not used since, according to one of his longtime friends. The U.S. Army confirmed that Loughner had been rejected as "unqualified" for Service in 2008. According to military sources, Loughner admitted to marijuana use on numerous occasions during the application process.

Loughner allegedly purchased the 9mm Glock pistol used in the shooting from a Sportsman's Warehouse in Tucson on November 30, 2010. The night before the shooting, at 2:05 a.m. he left a message on a friend's voicemail saying, "Hey man, it's Jared. Me and you had good times. Peace out. Later." In a MySpace post the morning of the shooting at 4:12 am, he wrote, "Goodbye friends. Please don't be mad at me. The literacy rate is below 5%. I haven't talked to one person who is literate. I want to make it out alive. The longest war in the history of the United States. Goodbye. I'm saddened with the current currency and job employment. I had a bully at school. Thank you. P.S. --plead the fifth!"

But, on July 12, 2011, a three-judge federal appeals panel from the Ninth Circuit ruled that Loughner could refuse anti-psychotic medication, since he "has not been convicted of a crime, is presumptively innocent and is therefore entitled to greater constitutional protections than a convicted inmate." However, the ruling stated that it "does not preclude prison authorities from taking other measures to maintain the safety of prison personnel, other inmates and Loughner himself, including forced administration of tranquilizers".

On November 8, 2012, Loughner appeared in front of U.S. District Court Judge Larry Alan Burns in a court in Tucson. He was sentenced to serve seven consecutive life terms plus 140 years in prison without parole. Even though he was convicted and sentenced in federal court, there was still a possibility that Loughner could be tried for murder and other crimes in Arizona court. Pima County Attorney Barbara LaWall declared later that afternoon that she would not prosecute Jared Loughner on behalf of the State of Arizona. LaWall explained that her decision would afford the victims and their families, as well as the community in Tucson and Pima County, an opportunity to move forward with their lives. She said that, after speaking and consulting personally with each of the surviving victims and with the family members of those killed, it was clear that they would not be benefitted by a State prosecution. Surviving victims and family members told LaWall that they are "completely satisfied with the federal prosecution", that "justice has been served", and that the federal sentence is "suitably severe".

Mark Potok of the Southern Poverty Law Center said that Loughner's position that currency not backed by a gold or silver standard is worthless was a "hallmark of the far right and the militia movement." Jesse Walker of Reason expressed deep skepticism at the connections drawn by Potok. In the aftermath of the shooting, the Anti-Defamation League reviewed messages by Loughner, and concluded that there was a "disjointed theme that runs through Loughner's writings", which was a "distrust for and dislike of the government." It "manifested itself in various ways" – for instance, in the belief that the government used the control of language and grammar to brainwash people, the notion that the government was creating "infinite currency" without the backing of gold and silver, or the assertion that NASA was faking spaceflights.