Russert was recording voiceovers for Sunday's "Meet the Press" program when he collapsed, the network said. No details were immediately available.
Russert, the recipient of 48 honorary doctorates, took over the helm of "Meet the Press" in December 1991. Now in its 60th year, "Meet the Press" is the longest-running program in the history of television.
In 2008, Time Magazine named him one of the 100 most influential people in the world.
Timothy John Russert Jr. was born in Buffalo, N.Y., on May 7, 1950. He was a graduate of Canisius High School, John Carroll University and the Cleveland-Marshall College of Law. He was a member of the bar in New York and the District of Columbia.
Senate staffer before entering journalism
After graduating from law school, Russert went into politics as a staff operative. In 1976, he worked on the Senate campaign of Daniel Patrick Moynihan, D-N.Y., and in 1982, he worked on Mario Cuomo's campaign for governor of New York.
Russert joined NBC News in 1984. In April 1985, he supervised the live broadcasts of NBC's TODAY show from Rome, negotiating and arranging an appearance by Pope John Paul II, a first for American television. In 1986 and 1987, Russert led NBC News' weeklong broadcasts from South America, Australia and China.
Of his background as a Democratic political operative, Russert said, "My views are not important."
"Lawrence Spivak, who founded ‘Meet the Press,' told me before he died that the job of the host is to learn as much as you can about your guest's positions and take the other side," he said in a 2007 interview with Time magazine. "And to do that in a persistent and civil way. And that's what I try to do every Sunday."
Cuomo, Russert's onetime boss, wrote of Russert: "Most candidates are not eager to present themselves for Tim's incisive scrutiny, which is fed by his prodigious study and preparation. But they have little choice: appearing on ‘Meet the Press' is today as vital to a serious candidate as being properly registered to vote."
Russert wrote two books - "Big Russ and Me" in 2004 and "Wisdom of Our Fathers" in 2006 - both of which were New York Times best-sellers.
Emmy for Reagan funeral coverage
In 2005, Russert was awarded an Emmy for his role in the coverage of the funeral of President Ronald Reagan. His "Meet the Press" interviews with George W. Bush and Al Gore in 2000 won the Radio and Television Correspondents' highest honor, the Joan S. Barone Award, and the Annenberg Center's Walter Cronkite Award.
Russert's March 2000 interview of Sen. John McCain shared the 2001 Edward R. Murrow Award for Overall Excellence in Television Journalism. He was also the recipient of the John Peter Zenger Award, the American Legion Journalism Award, the Veterans of Foreign Wars News Media Award, the Congressional Medal of Honor Society Journalism Award, the Allen H. Neuharth Award for Excellence in Journalism, the David Brinkley Award for Excellence in Communication and the Catholic Academy for Communication's Gabriel Award. He was a member of the Broadcasting & Cable Hall of Fame.
Russert was a trustee of the Freedom Forum's Newseum and a member of the board of directors of the Greater Washington Boys and Girls Club, and America's Promise - Alliance for Youth.
In 1995, the National Father's Day Committee named him "Father of the Year," Parents magazine honored him as "Dream Dad" in 1998, and in 2001 the National Fatherhood Initiative also recognized him as Father of the Year.
Irish America magazine named him one of the top 100 Irish Americans in the country, and he was selected as a Fellow of the Commission of European Communities.
Russert is survived by his wife, Maureen Orth, a writer for Vanity Fair magazine, and a son, Luke.