James Naismith (/ˈneɪsmɪθ/ NAY-smith; November 6, 1861 – November 28, 1939) was a Canadian-American physical educator, physician, Christian chaplain, and sports coach, best known as the inventor of the game of basketball.

While originally developing the game of basketball in Canada, after moving to the United States, he wrote the original basketball rule book and founded the University of Kansas basketball program in 1898. Naismith lived to see basketball adopted as an Olympic demonstration sport in 1904 and as an official event at the 1936 Summer Olympics in Berlin, as well as the birth of the National Invitation Tournament (1938) and the NCAA Tournament (1939).

Naismith studied and taught physical education at McGill University in Montreal until 1890, before moving to Springfield, Massachusetts, United States, later that year, where in 1891 he designed the game of basketball while he was teaching at the International YMCA Training School. Seven years after inventing basketball, Naismith received his medical degree in Denver in 1898. He then arrived at the University of Kansas, later becoming the Kansas Jayhawks' athletic director and coach.

While a coach at Kansas, Naismith coached Phog Allen, who later became the coach at Kansas for 39 seasons, beginning a lengthy and prestigious coaching tree. Allen then went on to coach players including Adolph Rupp and Dean Smith, who themselves coached many notable players and future coaches.

Naismith was born on November 6, 1861, in Almonte, Canada West, Province of Canada (now part of Mississippi Mills, Ontario, Canada) to Scottish parents. Despite some sources to the contrary, Naismith never had a middle name and never signed his name with an "A" initial. The "A" was added by someone in administration at the University of Kansas. Naismith spent his days outside playing catch, hide-and-seek, or duck on a rock, a medieval game in which a person guards a large skipping stone from opposing players, who try to knock it down by throwing smaller stones at it. To play duck on a rock most effectively, Naismith soon found that a soft lobbing shot was far more effective than a straight hard throw, a thought that later proved essential for the invention of basketball. Orphaned early in his life, Naismith lived with his aunt and uncle for many years and attended grade school at Bennies Corners near Almonte. Then, he enrolled in Almonte High School, in Almonte, Ontario, from which he graduated in 1883.

In the same year, Naismith entered McGill University in Montreal. Although described as a slight figure, standing 5 feet 10+1⁄2 inches (1.791 m) and listed at 178 pounds (81 kg) he was a talented and versatile athlete, representing McGill in football, lacrosse, rugby, soccer, and gymnastics. He played centre on the football team, and made himself some padding to protect his ears. It was for personal use, not team use. He won multiple Wicksteed medals for outstanding gymnastics performances. Naismith earned a BA in physical education (1888) and a diploma at the Presbyterian College in Montreal (1890). At the end of his career, in 1938 and 1939, he would receive honorary doctorates from both institutions. From 1888 to 1890, Naismith taught physical education and became the first McGill director of athletics, but then left Montreal to study at the YMCA International Training School in Springfield, Massachusetts. Naismith played football during his one year as a student at Springfield, where he was coached by Amos Alonzo Stagg and scored a touchdown in the first exhibition of indoor college football at Madison Square Garden.

Naismith is credited with inventing basketball. Having been an outstanding football player at McGill University in Montreal, he later decided to become a physical education teacher at McGill University for his three postgraduate years and then went to Springfield, Massachusetts, to study at the YMCA International Training School in the 1890s. Whilst teaching there, Naismith realized he needed to invent an indoor game for the winter due to the weather conditions.

After completing the YMCA physical director training program that had brought him to Springfield, Naismith was hired as a full-time faculty member in 1891. At the Springfield YMCA, Naismith struggled with a rowdy class that was confined to indoor games throughout the harsh New England winter, and thus was perpetually short-tempered. Under orders from then head of physical education Luther Gulick, Naismith was given 14 days to create an indoor game that would provide an "athletic distraction"; Gulick demanded that it would not take up much room, could help its track athletes to keep in shape and explicitly emphasized to "make it fair for all players and not too rough". Naismith was later employed to teach physical education using two boxes. He told the superintendent he needed the two boxes to be put onto a pole so a large ball could be thrown into them.