By Laila Kearney

(Reuters) - Pat Summitt, the winningest coach in U.S. Division I college basketball history, died on Tuesday at the age of 64, the University of Tennessee said.

Summitt, who coached the University of Tennessee's Lady Vols women's team and helped build women's college basketball into a national sport, announced in August 2011 that she had been diagnosed with early-onset dementia.

"Pat was the greatest coach of all time," university Chancellor Jimmy Cheek said in a statement. "Her fierce spirit will live on through her players and through all of us who were inspired by her on a daily basis."

Summitt died at Sherrill Hill Senior Living in Knoxville surrounded by her family, son Tyler Summitt said.

"Since 2011, my mother has battled her toughest opponent, early onset dementia, ‘Alzheimer’s Type,’ and she did so with bravely fierce determination, just as she did with every opponent she ever faced," he said in a statement. "We can all find peace in knowing she no longer carries the heavy burden of this disease."

Summitt was awarded the Presidential Medal of Freedom, the highest U.S. civilian honor, by President Barack Obama four years ago.

"Coach Summitt is an inspiration, both as the all-time winningest NCAA coach, and as someone who is willing to speak so openly and courageously about her battle with Alzheimer’s," the president said at the time.

Summitt was born on June 14, 1952 in Clarksville, Tennessee, the youngest of five children.

Growing up on a family farm, three older brothers taught her to play basketball, "a game that would later become a passion and profession for her," the Pat Summitt Foundation said.

Summitt received a bachelor's degree in physical education from the University of Tennessee-Martin in 1974, the same year she started coaching.

"People would refer to me as her boss and I always remarked, Pat Summitt has no boss," said Joan Cronan, the University of Tennessee director of women's athletics.

Known for her steely sideline demeanor and intense glare, Summitt recorded 1,098 career victories, the most in Division I college basketball history for a men's or women's coach, before stepping down in 2012. She coached the Lady Vols to eight national championships in her 38 seasons at the school.

She was named NCAA Coach of the Year seven times and the Naismith Coach of the Century in 2000.

Summitt and University of Connecticut women's basketball coach Geno Auriemma, who has won 11 titles, engaged in a storied rivalry for decades that elevated the sport to new heights. During the period from 1995 to 2010, the two schools combined to capture 12 championships.

"Lots of people coach the game. Very few get to define it," Auriemma said in an interview on ESPN on Tuesday.

Summitt also coached the 1984 U.S. Women’s Olympic team, which won the gold medal.

As a player, she was co-captain of the U.S. women’s basketball team, which won the silver medal at the Olympic Games in Montreal in 1976.

Summitt’s death sparked an outpouring of grief from the sports community on social media, and was the top-trending topic on Twitter in the United States.

"Thank you Pat Summitt for all you have done to inspire women to be their best self," tweeted Mia Hamm, a retired soccer player and two-time Olympic gold medalist. "This generation of women are forever changed b/c of you."

Summitt is survived by her mother, Hazel Albright Head; son, Ross “Tyler” Summitt; sister, Linda; brothers, Tommy, Charles and Kenneth.

A private funeral will be held in Middle Tennessee. A public memorial is planned at a later date at Thompson-Boling Arena at the University of Tennessee-Knoxville.

(Additional reporting by Joseph Ax and Amy Tennery; Editing by Jeffrey Benkoe)