After winning two U.S. Amateurs in 1959 and 1961, and challenging for the 1960 U.S. Open, Nicklaus turned professional toward the end of 1961. The 1962 U.S. Open was both Nicklaus' first major championship victory and his first professional win. This win over Arnold Palmer began the on-course rivalry between the two. In 1966, Nicklaus won the Masters Tournament for the second year in a row, becoming the first golfer to achieve this, and also won The Open Championship, completing his career slam of major championships; at 26, he became the youngest to do so at the time. After failing to win a major in 1968 and 1969, Nicklaus won another Open Championship in 1970.
Between 1971 and 1980, he would win a further nine major championships, overtake Bobby Jones' record of 13 majors, and become the first player to complete double and triple career slams of golf's four professional major championships. At the age of 46, Nicklaus claimed his 18th and final major championship at the 1986 Masters Tournament, becoming that championship's oldest winner. Nicklaus joined the Senior PGA Tour (now known as the Champions Tour) in January 1990, when he became eligible, and by April 1996 had won 10 of the tour's tournaments, including eight of that tour's major championships, despite playing a very limited schedule. He continued to play at least some of the four regular Tour majors until 2005, when he made his final appearances at The Open Championship and the Masters Tournament.
Nicklaus has also taken part in various off-course activities, including golf course design, charity work and book writing. Nicklaus also runs his own tournament on the PGA Tour, the Memorial Tournament. His golf course design company is one of the largest in the world. Nicklaus' books vary from instructional to autobiographical, with his Golf My Way considered one of the best instructional golf books of all time; the video of the same name is the best-selling golf instructional to date.