John Galsworthy (; 14 August 1867 – 31 January 1933) was an English novelist and playwright. He is best known for his trilogy of novels collectively known as The Forsyte Saga, and two later trilogies, A Modern Comedy and End of the Chapter. He won the Nobel Prize in Literature in 1932.

Born to a comfortable upper-middle class family, Galsworthy was destined for a career as a lawyer, but found it uncongenial and turned instead to writing. He was thirty before his first book was published in 1897, and did not achieve real success until 1906, when The Man of Property, the first of his novels about the Forsyte family was published. In the same year his first play, The Silver Box was staged in London. As a dramatist he became known for plays with a social message, reflecting among other themes, the struggle of workers against exploitation, the use of solitary confinement in prisons, the repression of women, and jingoism and the politics and morality of war.

The Forsyte family of the series of novels and short stories collectively known as The Forsyte Chronicles is similar in many ways to Galsworthy's family, and the patriarch, Old Jolyon, is modelled on his father. The main sequence runs from the late 19th century to the early 1930s, featuring three generations of the family. The books were popular when first published and their latter-day popularity was boosted considerably when BBC Television broadcast a 26-part adaptation for the author's centenary in 1967.

As well as writing plays and novels with social messages, Galsworthy campaigned continually for a wide range of causes about which he felt strongly, from animal welfare to prison reform, censorship and workers' rights. Although seen by many as a radical, he belonged to and supported no political party. His plays are seldom revived, but his novels have been frequently reissued.