Following the death of Muhammad Ali, golf's most successful player Jack Nicklaus expressed his long-term admiration for the boxing legend.

Ali, who battled Parkinson's disease for more than 30 years, passed away on Friday aged 74 as the world was left mourning the 'greatest of all time'.

Inspirational inside the ring, Ali was a three-time heavyweight champion, but the iconic American was a pioneer on the outside, leading the way for racial equality and social justice.

And 18-time major champion Nicklaus, who received the Muhammad Ali Legacy Award in December last year, paid tribute to his countryman, remembering the numerous meetings between the pair.

"My first meeting with Ali was [at the] PGA Championship in 1996," Nicklaus told CBS on Saturday. "We saw each other quite a bit at different events. I respected him greatly. He was a great champion. He did an awful lot for mankind.

"When he got his Parkinson's, there wasn't anything from a fighting standpoint he could do. But his life didn't end there. He did a lot of good for a lot of people. He was the champ. Always will be."

Nicklaus also released a statement, which read: "It is an understatement to say that today the hearts of the sports world are heavy with the loss of Muhammad Ali.

"He transcended not only the sport of boxing, but sports in general. He long ago established a legacy that crossed any boundaries of competition or the borders of just our country. He was a global icon.

"I was incredibly honoured and humbled to receive an award in December bearing his name. That night I told a story about how the walls in my home are not for plaques and trophies, but rather for photos of my kids and grandkids. Yet there is one special photo in my office, and that is of Muhammad and me playfully sparring at the PGA Championship in 1996 at Valhalla in his hometown of Louisville. I have always been a great fan of Muhammad, because I admired the champion he was in the ring and the champion he became out of the ring for so many causes.

"I hope on a day when we mourn the loss of the champ - the 'greatest of all time' - we can reflect and appreciate his many contributions past and present, and ensure that generations going forward will admire and be inspired by all that Muhammad Ali accomplished."