Former U.S. Sen. Jon Kyl, an Arizona Republican who spent nearly three decades in Congress and rose to become the Senate’s No. 2 Republican, died Wednesday at age 84.

Kyl’s family announced his death Thursday, citing complications from a neurological disease. The family disclosed in December 2025 that Kyl had been diagnosed with dementia and was stepping away from public life.

“We know that Jon belonged to all of Arizona, a state he loved and explored with vigor, curiosity, and wonder,” Kyl’s family wrote in a statement. “Serving his state and nation in Congress was a privilege and responsibility he honored and respected. We are grateful for his full and meaningful public life.”

Kyl was elected to the U.S. House in 1986 and took office in 1987. He represented Arizona in the House until 1995, when he began his first of three Senate terms. He was elected Senate Republican whip in 2007, a position he held until leaving the Senate in 2013.

Kyl briefly returned to the Senate in 2018 after former Gov. Doug Ducey appointed him to fill the vacancy created by Sen. John McCain’s death. Kyl served the final months of that session of Congress before resigning at year’s end.

“Jon Kyl gave Arizona nearly three decades of principled, thoughtful leadership — and he gave me something just as valuable: his mentorship and friendship,” Ducey wrote in a social media post. “I’ll miss him deeply.”

Kyl was also central to Arizona water policy. He was the principal sponsor of the Arizona Water Settlements Act, which Congress approved in 2004. 

The law authorized the Gila River Indian Community water rights settlement and amended the Southern Arizona Water Rights Settlement Act involving the Tohono O’odham Nation. The Bureau of Indian Affairs later credited Kyl as a key figure in bringing stakeholders together and shepherding the legislation through Congress.

“Whether he was negotiating complex water agreements or helping guide our nation’s security policy, Senator Kyl brought credibility, good judgment, and a determination to deliver results,” Senate President Warren Petersen, R-Gilbert, said in a Thursday statement. “He earned the respect of people across the political spectrum without compromising his principles.” 

Before he was elected to public office, Kyl also helped create Arizona’s 1980 Groundwater Management Act as an attorney representing Salt River Project. 

In a Thursday statement, Central Arizona Project General Manager Brenda Burman described Kyl as the driving force behind the 2004 water settlements act. Burman was a former staffer for Kyl while he was in Congress. 

“It is often said when working on Arizona water issues that we stand on the shoulders of giants that came before us. Senator Jon Kyl was one of those great Arizonans – a true statesman who served his state and country with dignity and honor,” Burman said. “He understood that water is the lifeblood of Arizona communities and his deep commitment to Arizona permanently shaped our state.

In 2006, TIME magazine named Kyl one of the best senators in the country and later included him on its 100 most influential people list in 2010. 

During his time in Congress, Kyl was considered one of the nation’s leaders in national security, serving as vice chair of the Congressional Commission on the Strategic Posture of the United States — a commission created to help prepare the U.S. for nuclear-armed adversaries.

The University of Arizona also honored Kyl earlier this year after it established the Kyl Institute for National Security. Kyl earned a bachelor’s degree from the university in 1964 and graduated from its James E. Rogers College of Law two years later. 

“The University of Arizona mourns the loss of Sen. Jon Kyl, and our thoughts are with his family during this difficult time,” said U of A President Suresh Garimella. “Sen. Kyl dedicated decades of his life to public service, and his record on national security and water policy left Arizona and the nation better than he found them. It is especially meaningful to us that his legacy continues at this university through the Kyl Institute for National Security, where his commitment to responsible governance lives on in the work of our students and researchers.”

News of Kyl’s death prompted a flurry of condolences from across the political spectrum.

Arizona’s Democratic Sen. Ruben Gallego called Kyl “a true statesman who often worked across the aisle for the good of all Arizonans.” Sen. Mark Kelly, also a Democrat, and Democratic former U.S. Rep. Gabrielle Giffords also released statements mourning his loss. Former Gov. Jan Brewer said in a post on X that Kyl “served our state and nation with extraordinary intellect, integrity and humility.”

Kyl’s family said in a statement that memorial services will be announced at a later date.