The sport, entertainment and political worlds are remembering boxing icon George Foreman’s legacy after his death at 76.

“Big George” was one of the great second acts in sports who reclaimed the heavyweight boxing title after coming out of retirement, a preacher and later a celebrated product pitchman.

“Condolences to George Foreman’s family. His contribution to boxing and beyond will never be forgotten,” two-time heavyweight champion Mike Tyson said.

“A humanitarian, an Olympian, and two time heavyweight champion of the world,” his family said, describing Foreman in a post on Instagram.

“He was deeply respected – a force for good, a man of discipline, conviction, and a protector of his legacy, fighting tirelessly to preserve his good name – for his family.”

George Foreman in Zaire, 1974. Photo: AAP

An intimidating, thunderous puncher who lost his first title to Muhammad Ali in their famous “Rumble in the Jungle” in 1974, “Big George” was a more rotund, jovial figure when he knocked out Michael Moorer for his second crown two decades later.

Foreman’s comeback and the fortune he made selling fat-wicking electric cooking grills made him an icon of self-improvement and success for the Baby Boomer generation.

Growing up poor in the segregated American South, Foreman dropped out of junior high school and used his size and fists in street robberies.

The Job Corps, part of President Lyndon B. Johnson’s “Great Society” reforms, “rescued me from the gutter,” Foreman later wrote. Through the program, 16-year-old Foreman moved out of Texas and was encouraged to channel his rage and growing bulk into boxing.

Foreman’s epic battle with Muhammad Ali is considered one of the greatest bouts of all time. Photo: AAP

At age 19 and in his 25th amateur fight, Foreman captured the heavyweight boxing gold medal at the 1968 Olympics in Mexico City.

Turning pro, he won 37 straight matches on his way to face reigning champion Joe Frazier in Kingston, Jamaica, winning by technical knockout in round two.

Foreman defended the belt twice more before meeting Ali in Kinshasa, Zaire, now the Democratic Republic of the Congo, in one of the most celebrated boxing matches in history.

Ali had been stripped of his crown seven years prior for refusing to be drafted into the Vietnam War and came into the match a heavy underdog against the bigger, younger champion.

But for seven rounds, Ali lay against the ropes and fended off Foreman’s clubbing blows, tiring and knocking him out in the eighth round.

“I was one strong heavyweight punching fighter,” Foreman told Reuters in 2007.

“I was one punching machine, and that was the first time I delivered everything I had and nothing worked.”

The loss devastated Foreman. He took a year off before returning to the ring and then, after a second professional loss, retired in 1977 to become an ordained minister in the Church of the Lord Jesus Christ.

A decade later and considerably heavier at 315 lbs (143 kg), Foreman staged an unlikely return to the ring to raise money for a youth centre he founded in Texas.

He went on to win 24 straight matches, gradually slimming along the way, before losing to Evander Holyfield in a 12-round decision in 1991. Three years later, he knocked out undefeated southpaw Moorer to become the oldest ever heavyweight champion at age 45.

Foreman’s last match was in 1997, ending his career with a professional record of 76 wins and five losses.

Foreman was married four times in the 1970s and 1980s. In 1985, he married for the fifth time to Mary Joan Martelly, with whom he remained for the rest of his life. He had five sons – all called George – five biological daughters, and two adopted daughters.

Throughout the 1990s and after retirement, he was an enthusiastic pitchman for various products, most notably an electric grill from home appliance maker Salton Inc.

George Foreman smiles as he talks about his son, George Foreman III. Photo: AAP

In 1999, the company paid Foreman and his partners $US137.5 million to put his name on the grill and other goods.

“What I do is fall in love with every product I sell,” Foreman wrote in his autobiography, “By George.”

“That’s what sells. Just like with preaching.”

Tributes flow

“Rest in peace, George Foreman. Your legacy lives on, champ.” – Scottie Pippen, six-time NBA champion

“I attended so many of George’s championship fights over his career. He was a knockout artist in the ring, and it was a pleasure getting to know him not only as a boxer but as a man. After leaving the ring, he turned into an amazing businessman – I even bought one of the first George Foreman grills!” – Magic Johnson, five-time NBA champion and entrepreneur

“RIP this hitting me tuff as George was one of my HEROES.” – Chuck D, rapper and co-founder of Public Enemy

“We have lost a true American legend. George Foreman was more than just a two-time heavyweight champion, he was a symbol of strength, resilience, faith, and redemption. From the ring to the pulpit, from Olympic gold to entrepreneurial greatness, George Foreman inspired generations with his story of perseverance and grace. Houston watched him rise with strength, humility, and an unshakable belief in God. Thank you for showing us what greatness truly looks like. Your legacy will live on forever.” – Wesley Hunt, Republican US representative from Texas

“Beyond a living legend in the ring – just a wonderful spirit – an incredibly kind generous man – in person. I always remember every encounter with great gratitude – it was an honour to know him.” – John Cusack, actor

“George was a great friend to not only myself, but to my entire family. We’ve lost a family member and are absolutely devastated.” – Bob Arum, boxing promoter

“I got to know Mr Foreman a little bit, seeing him at all the boxing matches and I always picked his brain about trying to be an entrepreneur when your career is over. It hurts a lot because he was obviously one of the greatest boxers ever, but just a gentle man, was a pastor. This just hurts.” – Charles Barkley, Hall of Fame NBA player

“Good case to be made that George Foreman fashioned the greatest second act in sports history. And it was more than reclaiming the title. It was a total transformation.” – Jeremy Schaap, ESPN journalist

“In 1973, I was honoured to welcome Foreman to the State Capitol along with my then-colleague, Mickey Leland. The world knew Foreman as a two-time heavyweight champion; we knew him as a proud member of our community – a man whose heart was as big as his powerful punch. George’s journey from the streets of Fifth Ward to boxing and business success was an inspiration. He never forgot where he came from, and his commitment to our city was constant.” – John Whitmire, mayor of Houston

—AAP