Robert Leroy Johnson (May 8, 1911 – August 16, 1938) was an American blues musician and songwriter. His singing, guitar playing and songwriting on his landmark 1936 and 1937 recordings have influenced later generations of musicians. Although his recording career spanned only seven months, he is recognized as a master of the blues, particularly the Delta blues style, and as one of the most influential musicians of the 20th century. The Rock and Roll Hall of Fame describes him as perhaps "the first ever rock star".

As a traveling performer who played mostly on street corners, in juke joints, and at Saturday night dances, Johnson had little commercial success or public recognition in his lifetime. He had only two recording sessions both produced by Don Law, one in San Antonio in 1936, and one in Dallas in 1937, that produced 29 distinct songs (with 13 surviving alternate takes). These songs, recorded solo in improvised studios, were the sum of his recorded output. Most were released as 10-inch, 78 rpm singles from 1937–1938, with a few released after his death. Other than these recordings, very little was known of his life outside of the small musical circuit in the Mississippi Delta where he spent most of his time. Much of his story has been reconstructed by researchers. Johnson's poorly documented life and death have given rise to legends. The one most often associated with him is that he sold his soul to the devil at a local crossroads in return for musical success.

His music had a small, but influential, following during his life and in the decades after his death. In late 1938, John Hammond sought him out for a concert at Carnegie Hall, From Spirituals to Swing, only to discover that Johnson had recently died. Hammond was a producer for Columbia Records which bought Johnson's original recordings from Brunswick Records which owned them. The musicologist Alan Lomax went to Mississippi in 1941 to record Johnson, also not knowing of his death. In 1961, Columbia released an album of Johnson's recordings titled King of the Delta Blues Singers, produced by legendary producer and music historian Frank Driggs. It is credited with finally bringing Johnson's work to a wider audience. The album would become influential, especially in the nascent British blues movement; Eric Clapton called Johnson "the most important blues singer that ever lived". Bob Dylan, Keith Richards, and Robert Plant have cited both Johnson's lyrics and musicianship as key influences on their own work. Many of Johnson's songs have been covered over the years, becoming hits for other artists, and his guitar licks and lyrics have been borrowed by many later musicians.

Renewed interest in Johnson's work and life led to a burst of scholarship starting in the 1960s. Much of what is known about him was reconstructed by researchers such as Gayle Dean Wardlow and Bruce Conforth, especially in their 2019 award-winning biography of Johnson: Up Jumped the Devil: The Real Life of Robert Johnson (Chicago Review Press). Two films, the 1991 documentary The Search for Robert Johnson by John Hammond Jr., and a 1997 documentary, Can't You Hear the Wind Howl?: The Life & Music of Robert Johnson, which included reconstructed scenes with Keb' Mo' as Johnson, attempted to document his life, and demonstrated the difficulties arising from the scant historical record and conflicting oral accounts. Over the years, the significance of Johnson and his music has been recognized by the Rock and Roll, Grammy, and Blues Halls of Fame, and by the National Recording Preservation Board.

Robert Leroy Johnson was born in Hazlehurst, Mississippi, possibly on May 8, 1911, to Julia Major Dodds (born October 1874) and Noah Johnson (born December 1884). Julia was married to Charles Dodds (born February 1865), a relatively prosperous landowner and furniture maker, with whom she had ten children. Charles Dodds had been forced by a lynch mob to leave Hazlehurst following a dispute with white landowners. Julia left Hazlehurst with baby Robert, but in less than two years she took the boy to Memphis to live with her husband, who had changed his name to Charles Spencer. Robert spent the next 8–9 years growing up in Memphis and attending the Carnes Avenue Colored School where he received lessons in arithmetic, reading, language, music, geography, and physical exercise. It was in Memphis that he acquired his love for, and knowledge of, the blues and popular music. His education and city upbringing placed him apart from most of his contemporary blues musicians.

Robert rejoined his mother around 1919–1920 after she married an illiterate sharecropper named Will "Dusty" Willis. They originally settled on a plantation in Lucas Township in Crittenden County, Arkansas, but soon moved across the Mississippi River to Commerce in the Mississippi Delta, near Tunica and Robinsonville. They lived on the Abbay & Leatherman Plantation. Julia's new husband was 24 years her junior. Robert was remembered by some residents as "Little Robert Dusty", but he was registered at Tunica's Indian Creek School as Robert Spencer. In the 1920 census, he is listed as Robert Spencer, living in Lucas, Arkansas, with Will and Julia Willis. Robert was at school in 1924 and 1927. The quality of his signature on his marriage certificate suggests that he was relatively well educated for a man of his background. A school friend, Willie Coffee, who was interviewed and filmed in later life, recalled that as a youth Robert was already noted for playing the harmonica and jaw harp. Coffee recalled that Robert was absent for long periods, which suggests that he may have been living and studying in Memphis.

Once Julia informed Robert about his biological father, Robert adopted the surname Johnson, using it on the certificate of his marriage to fourteen-year-old Virginia Travis in February 1929. She died in childbirth shortly after. Surviving relatives of Virginia told the blues researcher Robert "Mack" McCormick that this was a divine punishment for Robert's decision to sing secular songs, known as "selling your soul to the Devil". McCormick believed that Johnson himself accepted the phrase as a description of his resolve to abandon the settled life of a husband and farmer to become a full-time blues musician.

Around this time, the blues musician Son House moved to Robinsonville, where his musical partner Willie Brown lived. Late in life, House remembered Johnson as a little boy who was a competent harmonica player but an embarrassingly bad guitarist. Soon after, Johnson left Robinsonville for the area around Martinsville, close to his birthplace, possibly searching for his natural father. Here he mastered the guitar style of House and learned other styles from Isaiah "Ike" Zimmerman. Zimmerman was rumored to have learned supernaturally to play guitar by visiting graveyards at midnight. When Johnson next appeared in Robinsonville, he seemed to have miraculously developed a mature guitar technique. House was interviewed at a time when the legend of Johnson's pact with the devil was well known among blues researchers. He was asked whether he attributed Johnson's technique to this pact, and his equivocal answers have been taken as confirmation.