Muhammad Ali was — and still is — the greatest. In honor of his 70th birthday, here's a look back at Ali's work in and out of the ring.

Ali was born Cassius Clay and won several bouts, including this victory in 1964 against Sonny Liston, before changing his name when he joined the Nation of Islam that same year.

Muhammad Ali refusal to fight in Vietnam in 1967, a move that gained him support among other prominent athletes. In this photo, he's seen with athletes including (front row, from left) Bill Russell, Jim Brown, and Lew Alcindor (who changed his name to Kareem Abdul-Jabbar).

Muhammad Ali gets ready during a training session in Frankfurt, Germany in 1966. He recorded a TKO win over Karl Mildenberger in the city in September of that year.

Muhammad Ali puts 'em up for cameras during a training session in Frankfurt in 1966.

Muhammad Ali (left) stares down Joe Frazier during a 1974 fight at Madison Square Garden. Ali won by unanimous decision. The boxers faced off in two other legendary bouts: The Fight of the Century in 1971, which was won by Frazier, and the 1976 Thrilla in Malina, which Ali won.

Muhammad Ali holds up a poster during a promotional event in Paris to promote his famous "Rumble in the Jungle" with George Foreman in 1974.

Muhammad Ali signs autographs in Paris in 1974 ahead of his famous "Rumble in the Jungle" fight.

Muhammad Ali throws a punch at George Foreman during the 1974 "Rumble in the Jungle." Ali beat Foreman in a knockout.

Muhammad Ali (right) battles Larry Holmes (left) in their WBC heavyweight title fight at Caesars Palace in 1980. Holmes defeated Ali in the 10th round that night, and Ali faced only one more fight before calling it a career.

Muhammad Ali stands with boxing promoter Don King in Las Vegas. King promoted Ali's "Rumble in the Jungle" and "Thrilla in Manila" bouts during his career.

Muhammad Ali holds the torch before lighting the Olympic Flame during the Opening Ceremony of the 1996 Olympic Games in Atlanta. The boxer won a gold medal for the U.S. at the 1960 Olympic Games in Rome.

U.S. President George W. Bush presents Muhammad Ali with the Medal of Freedom during a ceremony in 2005.

Laila Ali followed in her father's footsteps, becoming a successful boxer in her own right. Ali poses here with her father after winning a bout in 2002.

New York Yankees shortstop Derek Jeter (right) shakes hands with Muhammad Ali at Yankee Stadium in 2009. Ali fought Ken Norton there in 1976.