No cause of death was reaveled ... but Reed had been ill, battling congestive heart failure, longtime NYC columnist Peter Vescey reported.

"The Knicks organization is deeply saddened to announce the passing of our beloved Captain, Willis Reed," the Knicks said in a statement. "As we mourn, we will always strive to uphold the standards he left behind -- the unmatched leadership, sacrifice and work ethic that personified him as a champion among champions."

"His is a legacy that will live forever. We ask everyone to please respect the family’s privacy during this difficult time."

Simply put, Willis was one of the best hoopers to ever step foot on the hardwood.

Reed, a 6'10" center, was drafted by the Knicks with the tenth overall pick in the 1964 NBA Draft. Over his 10-season career, he averaged nearly 19 points and 13 rebounds. Willis was a 7x All-Star, 2x NBA Finals MVP and the 1970 NBA MVP.

Willis' most famous moment came during Game 7 of the 1970 NBA Finals. The Knicks and Lakers were knotted at three games apiece, with the title on the line. Reed missed Game 6 with a severe thigh injury, and almost no one expected the big man to play in the deciding game.

But, to the amazement of thousands of fans at Madison Square Garden, Reed limped onto the court during warmups, prompting the crowd to erupt. Willis hit the first two shots for the Knicks, and it was the only time he scored in the game.

However, Reed's presence gave his Knicks teammates the lift they needed to down Wilt Chamberlain, Elgin Baylor, and Jerry West's Lakers squad, 113-99. It was the Knickerbockers' first title.

NYK then won another championship three years later in 1973.

After retiring from the NBA in '74, Reed was hired by the Knicks as head coach in '77. His coaching stint in NY didn't last very long. In 1981, Willis went back to college, where he coached Creighton. He then had stints as an assistant coach with the Atlanta Hawks and Sacramento Kings.

In 1988, Reed was again named an NBA head coach when he was hired as the New Jersey Nets' headman.

The Knicks' last title was in 1973 ... and the franchise recently celebrated the 50-year anniversary, welcoming back stars from the team like Walt Frazier. Sadly, Reed, because of health issues, wasn't able to make it to NYC for the event.

The Garden played a pretaped message from the legendary hooper ... and the crowd loved it.

NBA commish Adam Silver released a statement on the legend's passing ... saying, "Willis Reed was the ultimate team player and consummate leader."

"My earliest and fondest memories of NBA basketball are of watching Willis, who embodied the winning spirit that defined the New York Knicks' championship teams in the early 1970s. He played the game with remarkable passion and determination, and his inspiring comeback in Game 7 of the 1970 NBA Finals remains one of the most iconic moments in all of sports."

"We send our deepest condolences to Willis' wife, Gail, his family and his many friends and fans."

He may now be gone ... but Reed's #19 will forever hang in the rafters of the World's Most Famous Arena.