Martinson was born in Jämshög, Blekinge County in south-eastern Sweden. At a young age he lost both his parents whereafter he was placed as a foster child (Kommunalbarn) in the Swedish countryside. At the age of sixteen Martinson ran away and signed onto a ship to spend the next years sailing around the world visiting countries such as Brazil and India.

A few years later lung problems forced him to set ashore in Sweden where he travelled around without a steady employment, at times living as a vagabond on country roads. In the city of Malmö, at the age of 21, he was arrested for vagrancy.

In 1929, he debuted as a poet. Together with Artur Lundkvist, Gustav Sandgren, Erik Asklund and Josef Kjellgren he authored the anthology Fem unga (Five Youths), which introduced Swedish Modernism. His poetry combined an acute eye for, and love of nature, with a deeply-felt humanism. His popular success as a novelist came with the semi-autobiographical Nässlorna blomma (The Nettles Flower) in 1935, about hardships encountered by a young boy in the countryside. It has since been translated into more than thirty languages.

One of his most famous works is the poetic cycle Aniara, which is a story of the space craft Aniara that during a journey through space loses its course and subsequently floats on without destination. The book was published in (1956) and became in 1959 an opera composed by Karl-Birger Blomdahl. The cycle has been described as an epic story of man's fragility and folly.

From 1929 to 1940 he was married to the Swedish writer Moa Martinson. The sensitive Harry found criticism in the 1970s subsequent to the Nobel prize hard to cope with, and attempted suicide with a pair of scissors. He died of February 11, 1978, in Gnesta.

The 100th anniversary of Martinson's birth was celebrated around Sweden in 2004.

Titles in English where known.

Novels

• Vägen till Klockrike (The Road)
• Nässlorna blomma (Flowering Nettles)
• Vägen ut (The Way Out)

Essays

• Svärmare och harkrank
• Midsommardalen (Midsommer valley)
• Det enkla och det svåra (The easy and the hard)
• Utsikt från en grästuva (Views From A Tuft of Grass)
• Verklighet till döds (Reality to death)
• Den förlorade jaguaren (The Lost Jaguar)
• Resor utan mål (Aimless Journeys)

Poems

• Spökskepp
• Nomad
• Passad (Trade Wind)
• Cikada
• Aniara
• Gräsen i Thule
• Vagnen
• Dikter om ljus och mörker
• Tuvor

Radio plays

• Gringo
• Salvation
• Lotsen från Moluckas

Stage play

• Tre knivar från Wei

Psalms

• De blomster som i marken bor