Jens Peter Jacobsen (7 April 1847 – 30 April 1885) was a Danish novelist, poet, and scientist, in Denmark often just written as "J. P. Jacobsen" and pronounced as "I. P. Jacobsen". He began the naturalist movement in Danish literature and was a part of the Modern Break-Through.

Jacobsen was born in Thisted in Jutland as the eldest of the five children of a prosperous merchant. Jacobsen went to school in Copenhagen and later became a student at the University of Copenhagen in 1868. As a boy, he showed a remarkable talent for science, particularly for botany. In 1870, although he was secretly writing verses already, Jacobsen adopted botany as a profession. He was sent by a scientific body in Copenhagen to report on the flora of the islands of Anholt and Læsø. About this time, the discoveries of Charles Darwin began to exercise a fascination over him, and finding them little understood in Denmark, he translated into Danish The Origin of Species and The Descent of Man. Very early he was struck by tuberculosis which ended his life and made long travels to Southern Europe a necessity.

The fine literary work of Jacobsen is small: two novels, seven short-stories, and one volume of posthumous poems, but it places him as one of the most influential Danish writers. The historical novel Fru Marie Grubbe (1876, Eng. transl.: Marie Grubbe. A Lady of the seventeenth Century 1917) is the first Danish tale to treat woman as a sexual creature. Based upon the fate of an authentic Danish noblewoman of the 17th century it tells about her social deroute from being a member of the royal house to being the wife of a ferryman, all due to her wish of an independent and satisfying erotic life. In many ways the books anticipates the themes of D. H. Lawrence. - Jacobsen's second novel Niels Lyhne (1880, Engl. transl. 1919) describes the hard fate of the atheist in a merciless world; his lack of faith is "tested" by tragedies and personal crises until he dies in war, disillusioned but unyielding. - The Jacobsen short stories are collected in Mogens og andre Noveller (1882, Engl. transl. Mogens and Other Tales, 1921). Among them must be mentioned Mogens (1872 - his official debut), the tale of a young dreamer and his maturing during love, sorrow and new hope of love. Et Skud i Taagen (A Shot in the Fog) is a Poe-inspired tale of the sterility of hatred and revenge. Pesten i Bergamo (The Plague of Bergamo) shows the peoples' clinging to religion even when tempted to be "free men". Fru Fønss (1882) is a sad story about a widow's tragic break with her egoistic children when she wants to remarry.

The poems of Jacobsen are more influenced by late romanticism than his prose. Many of them are wistful, dreaming and melancholic but on the other hand standing on the ground of naturalist thinking. Most important is the great obscure poem Arabesque to a Hand-drawing by Michel Angelo (about 1875) whose idea seems to be that art is going to replace immortality as the meaning of life. They have been a main inspiration of Danish symbolist poetry of the 1890s.

Unlike many of his colleagues Jacobsen did not take much part in politics, his main interests were science and psychology. First of all he is the artist. His ability of creating "paintings" and arabesque-like scenes both in his prose and his poetry (which has sometimes been criticized as being "mannered") is one of the secrets behind his art. It has been said that his novels are a presentation of various snapshots more than tales with an action.

In spite of his not very extensive work Jacobsen's international influence is rather strong. In Germany both his novels and poems were widely read and they are known to have influenced both Rilke and Thomas Mann just as it has probably made impression on Lawrence. Even musical life has been influenced: Delius' Fennimore and Gerda and Arnold Schönberg's Gurre-Lieder are based upon themes from Jacobsen's books.

Jacobsen works in English

• J. P. Jacobsen: Marie Grubbe. A Lady of the Seventeenth Century. Gloucester, Mass., 1975.
• J. P. Jacobsen: Mogens and other Stories. Seattle, 1994.
• J. P. Jacobsen: Niels Lyhne. Seattle, 1990.