Dale Carnegie (November 24, 1888 – November 1, 1955) was an American writer and lecturer, and the developer of courses in self-improvement, salesmanship, corporate training, public speaking, and interpersonal skills. Born into poverty on a farm in Missouri, he was the author of How to Win Friends and Influence People (1936), a bestseller that remains popular today. He also wrote How to Stop Worrying and Start Living (1948), Lincoln the Unknown (1932), and several other books.

One of the core ideas in his books is that it is possible to change other people's behavior by changing one's behavior towards them.

Dale Carnegie was born November 24, 1888, on a farm in Maryville, Missouri. He was the second son of farmers James William Carnagey (1852–1941) and his wife Amanda Elizabeth Harbison (1858–1939). Carnegie grew up around Bedison, Missouri southeast of Maryville and attended rural Rose Hill and Harmony one room schools. Carnegie would develop a longstanding friendship with another Maryville author, Homer Croy.

In 1904, at age 16, his family moved to a farm in Warrensburg, Missouri. As a youth, he enjoyed speaking in public and joined his school's debate team. Carnegie said he had to get up at 3 a.m. to feed the pigs and milk his parents' cows before going to school. During high school, he grew interested in the speeches at the various Chautauqua assemblies. He completed his high school education in 1906.

He attended State Teacher's College in Warrensburg, graduating in 1908.

His first job after college was selling correspondence courses to ranchers. He moved on to selling bacon, soap, and lard for Armour & Company. He was successful to the point of making his sales territory of South Omaha, Nebraska, the national leader for the firm.

After saving $500, Dale Carnegie quit sales in 1911 in order to pursue a lifelong dream of becoming a Chautauqua lecturer. He ended up instead attending the American Academy of Dramatic Arts in New York, but found little success as an actor, though it is written that he played the role of Dr. Hartley in a road show of Polly of the Circus. When the production ended, he returned to New York, living at the YMCA on 125th Street. There he got the idea to teach public speaking, and he persuaded the YMCA manager to allow him to instruct a class in return for 80% of the net proceeds. In his first session, he had run out of material. Improvising, he suggested that students speak about "something that made them angry", and discovered that the technique made speakers unafraid to address a public audience. From this 1912 debut, the Dale Carnegie Course evolved. Carnegie had tapped into the average American's desire to have more self-confidence, and by 1914, he was earning $500 (about $13500 today) every week.

During World War I he served in the U.S. Army spending the time at Camp Upton. His draft card noted he had filed for conscientious objector status and had a loss of a forefinger.

By 1916, Dale conducted a sold out lecture at Carnegie Hall, which influenced his decision in 1919 to change the spelling of his last name in honor of the steel magnate, Andrew Carnegie, and easier for others to remember. Carnegie's first collection of his writings was Public Speaking: a Practical Course for Business Men (1926), later entitled Public Speaking and Influencing Men in Business (1932). In 1936, Simon & Schuster published How to Win Friends and Influence People. The book was a bestseller from its debut. By the time of Carnegie's death, the book had sold five million copies in 31 languages, and there had been 450,000 graduates of his Dale Carnegie Institute. It has been stated in the book that he had critiqued over 150,000 speeches in his participation in the adult education movement of the time.