Hank Kaplan, widely regarded as the nation’s foremost boxing historian, one whose encyclopedic knowledge of the sport made him indispensable to generations of journalists and filmmakers, died December 14 of cancer at his home in Kendall, Fla. He was 88. As a young man, Kaplan competed in one professional fight — which he won — and then turned his attention to documenting the colorful past of the sport known as “the sweet science.”

He amassed a priceless collection of books, publications, photographs, and memorabilia, which he kept at his home just outside Miami.

He attended his first professional fight at 14 and remained a fixture at boxing gyms and championship bouts for decades. Boxers and writers dubbed him “the sweet scientist,” “the human encyclopedia,” and “the Lord of the Ring.”

In the 1950s and 1960s, he was a publicist for the brothers Chris and Angelo Dundee, who molded the careers of Muhammad Ali and other champions, and he occasionally promoted fights on his own. He wrote dozens of articles and edited books and magazines, but the scholarly, pipe-smoking Kaplan mostly served as a reliable and eloquent source of information about boxing’s storied and checkered history.

He kept detailed records on virtually every professional boxer and trainer in history and had files on all manner of what he might call, in his deliberately orotund way, fistic arcana: unorthodox training methods; boxing in the movies; animals in boxing; bareknuckle fighting, and Jewish and Italian boxers who adopted Irish names.

“I think Hank is one of a kind,” a former boxing writer for Sports Illustrated, Pat Putnam, told the Miami New Times in 1998. “I just don’t see how anyone could know as much as he knows.”

For decades, Kaplan was on retainer to Sports Illustrated and also served as a historian for HBO, Showtime, and ESPN. He was almost never stumped by a question, and if he didn’t know the answer, he promised to find it within 10 minutes.

One time, a radio station offered a free dinner to anyone who could trip him up. When a caller asked which fight was the first to be broadcast nationwide on radio, Kaplan replied that it was the Frankie Burns-Packey O’Gatty bantamweight match of July 2, 1921. The caller corrected him, saying it was heavyweight champion Jack Dempsey’s bout with Georges Carpentier.

“No, that was the first title fight,” Kaplan replied. “The first fight broadcast that night was Burns and O’Gatty. They were on the undercard.”

Kaplan knew practically every boxing champion of the 20th century, including Dempsey, Joe Louis, Rocky Marciano, Henry Armstrong, Jake LaMotta, Sugar Ray Robinson, and Sugar Ray Leonard. He was especially close to Ali, whom he first met in 1960 when the 18-year-old future heavyweight champion — then known as Cassius Clay — began his professional career at the Fifth Street Gym in Miami Beach.

Despite his association with big-name boxers, Kaplan was particularly keen on maintaining the public memory of such forgotten fighters as Fritzie Zivic, Bob Satterfield, Kid Chocolate, Beau Jack, Eddie O’Keefe, and Joe Grim, whose record of 6-91-9 was the worst of all time.

“Even when I was 16 or 17, I said there’s got to be some way to remember them,” Kaplan told the South Florida Sun-Sentinel in 1995. “If someone were to ask me why I keep the archives, I guess that’s what I’d say: Someone has to be charged with remembering them.”

Kaplan was born April 15, 1919, in Brooklyn, N.Y., and spent much of his childhood in an orphanage after his father died. He became interested in boxing when his nose was bloodied at a summer camp.

When he learned that Dempsey had become the Coast Guard’s director of physical training during World War II, “I rushed down to the recruiting station.”

He disinfected ships and was eventually assigned to the U.S. Public Health Service, and later the Centers for Disease Control and Prevention, based in Miami. He attended the University of Miami at night while inspecting ships and airplanes by day for signs of tropical and infectious disease. He once spent nine weeks in Indonesia helping to stop an outbreak of bubonic plague.

After retiring from the CDC at 55, Kaplan devoted his full attention to boxing. He edited the World-Wide Boxing Digest in the late 1970s but spent most of his time attending to his growing collection. He owned every edition of Ring magazine as well as foreign boxing journals and books dating to 1812. His 500,000 boxing photographs are believed to be the largest collection in the world.

In 1989, Kaplan helped establish the International Boxing Hall of Fame in Canastota, N.Y. He set up its research library and served for years on its nominating committee, from which he had to resign before he could be elected to the Hall of Fame in 2006.

Often asked to name the greatest boxers of all time, Kaplan preferred to describe particular qualities he admired. Louis, he said, was the finest boxing stylist; Marciano had the biggest heart; Robinson had the finest combination of skills; Ali was “the greatest innovator in the history of boxing.” When pressed, Kaplan invariably cited a featherweight champion of the 1940s whose defensive skills allowed him to win 230 of 242 professional fights.

“Willie Pep,” Kaplan said, “was the greatest boxer ever. There’s nobody even close to him today.” Kaplan’s wife of 56 years, Sylvia Kaplan, died last year.

Survivors include his daughter and a son, Steven Kaplan, both of Miami; a brother, and two granddaughters.

Last year, Kaplan reached an agreement to have his archives transferred to Brooklyn College.