Harry Martinson (6 May 1904 – 11 February 1978) was a Swedish writer, poet and former sailor. In 1949 he was elected into the Swedish Academy. He was awarded a joint Nobel Prize in Literature in 1974 together with fellow Swede Eyvind Johnson "for writings that catch the dewdrop and reflect the cosmos". The choice was controversial, as both Martinson and Johnson were members of the academy.

He has been called "the great reformer of 20th-century Swedish poetry, the most original of the writers called 'proletarian'." One of his most noted works is the poetic cycle Aniara, which is a story of the spacecraft Aniara that during a journey through space loses its course and subsequently floats on without destination. The book was published in 1956 and became an opera in 1959 composed by Karl-Birger Blomdahl. The cycle has been described as "an epic story of man's fragility and folly".

Martinson was born in Jämshög, Blekinge County in south-eastern Sweden. Born Harry Edmund Olofsson, he was the fifth child of middle class parents who ran a small shop in the village Nyteboda and had four older and two younger sisters. At a young age he lost both his parents, his father died of tuberculosis in 1910 and a year later his mother emigrated to Portland, Oregon leaving behind her children, whereafter Martinson was placed as a foster child (Kommunalbarn) in the Swedish countryside. He was moved between different homes and alternated between working for his foster parents and attending elementary school, where he often received excellent grades. Martinson would later depict his childhood in the novel Flowering Nettle (1935), and its continuation Vägen ut ("The Way Out", 1936).

At the age of sixteen Harry Martinson, as he now called himself, had run away and signed onto a ship in Gothenburg as an able seaman. The steam ship's journey reached France, Ireland and Scotland, but after returning to Stockholm Martinson signed off as he could not afford the necessary winter clothes. He then spent eighteen months as a vagrant, eventually reaching as far as Umeå in north-east Sweden and then Tromsø in northern Norway. In June 1921 he was arrested for vagrancy in Lundagård park, Lund. In March 1922 he signed on as a stoker on a steam ship that sailed to Norway and Iceland, but after two months he ran away in Belgium. He stayed in Antwerpen, Belgium for a while before signing on to a ship destined for USA, where he hoped to meet his mother, and then to a Greek ship sailing to South America. He spent some time as a seaman in Brazil and then signed on to a ship that sailed from Rio de Janeiro to Cape Town, and then further to Bombay. In Bombay he again ran away, before signing on to another ship that sailed back to Europe.

Troubled by lung problems Martinson set ashore in Sweden on his 23rd birthday in May 1927. Martinson would later depict his years as a seaman in several acclaimed books, including Kap farväl! (1933), which was a critical and commercial success and the first of his books to be translated to English (Cape Farewell, 1934).

Around 1927, Martinson began his literary career and had several poems published in different publications. The same year he met Artur Lundkvist, who introduced him to modernist poets such as Elmer Diktonius, Carl Sandburg and Edgar Lee Masters. In September 1929, Martinson's first book of poems called Spökskepp ("Ghost Ship") was published by Albert Bonniers förlag. Together with Lundkvist, Gustav Sandgren, Erik Asklund and Josef Kjellgren he authored the anthology Fem unga (Five Youths), which introduced modernism in Swedish literature. His next collection of poems, Nomad (1931) featured a wide scope of themes and literary styles, including nature poems, impressions from his sea travels and childhood memories and mixed traditional rhymed verse with modernist free verse and epic prose poems. It was widely acclaimed by contemporary critics and is regarded as Martinson's literary breakthrough. It was followed by two prose books in which Martinson recalled his years as a seaman, Resor utan mål ("Aimless Journeys", 1932) and Kap farväl! (Cape Farewell, 1933) which further established Martinson as one of the leading Swedish authors of his generation.

After a poorly received collection of poems, Natur ("Nature", 1934), Martinson found great success as a novelist with the semi-autobiographical Nässlorna blomma (Flowering Nettle) in 1935, in which he depicted his childhood. It was a critical and widely read success that at the end of 1935 had been published in three editions, and has since been translated into more than thirty languages. The story was continued in the novel Vägen ut ("The Way Out") in 1936, which was another critical and commercial success.

The commercial success of his recent books and several scholarships awarded for his writing allowed Martinson to buy a farm in Södermanland, where he lived with his wife, the proletarian novelist Moa Martinson, and her sons. During this time he wrote a trilogy of essay books that focused on nature: Svärmare och harkrank (1937), Midsommardalen (1938) and Det enkla och det svåra (1939).