Antoni Lange (28 April 1862 – 17 March 1929) was a Polish poet, philosopher, polyglot (15 languages), writer, novelist, science-writer, reporter and translator. A representative of Polish Parnassianism and symbolism, he is also regarded as belonging to the Decadent movement. He was an expert on Romanticism, French literature and a popularizer of Eastern cultures. His most popular novel is Miranda.

He translated English, French, Hungarian, Italian, Spanish, Indian, American, Serbian, Egyptian and Oriental writers into Polish and Polish poets into French and English. He was also one of the most original poets of the Young Poland movement. His work is often compared to Stéphane Mallarmé and Charles Marie René Leconte de Lisle.

Lange was an uncle of the poet Bolesław Leśmian.

Lange was born in Warsaw into the patriotic Jewish family of Henryk Lange (1815–1884) and Zofia née Eisenbaum (1832–1897). His father took part in the November Uprising against the Russian Partition of Poland. He was an admirerer of Romantic literature and its ideals. Antoni Lange enrolled at Warsaw University but around 1880 he was expelled for his patriotic activity by the Tsarist namiestnik Apuchtin who ruled the university at that time. He supported himself financially as a tutor but also published poetry under the pen-names Napierski and Antoni Wrzesień. He decided to study in Paris where he encountered new trends in literature, philosophy and art. In France he became familiar with the theories of Jean Martin Charcot, as well as Spiritualism, parapsychology, the philosophy of Arthur Schopenhauer and Friedrich Nietzsche, oriental religions, European and Eastern literature and modern literary criticism. He took part in the literary meetings of Stéphane Mallarmé.

Lange returned to his homeland upon Poland's return to independence, and became one of the better known members of the Warsaw Society of Writers and Journalists (Warszawskie Towarzystwo Literatów i Dziennikarzy), the precursor of the Polish Academy of Literature founded in 1933. Bolesław Prus, Julian Ochorowicz and Lange were the first Polish spiritists. He rented an apartment at Nowy Świat Street together with Władysław Reymont, a Polish writer and the winner of the Nobel Prize of 1924. Stanisław Brzozowski called Lange a real and not frequently European mind and Julian Tuwim called him a master of reflective poetry. During this time Lange was a member of the Society of Polish Writers and Journalists. However, with the sharp growth of his popularity as a poet his poems became more sceptical, pessimistic and hermetic. The main theme of the poems of this period was the feeling of being isolated and misunderstood by the crowd.

At the beginning of the 20th century he withdrew from public life and became lonely and forgotten. He collected his last poems in notebooks and never allowed anyone to publish them.

Lange's prestige as a writer was undermined by a new generation of avant-gardists. He died in isolation, destitution and obscurity in Warsaw in 1929. He never married and had no children.

Antoni Lange was a friend of Stéphane Mallarmé, Jan Kasprowicz and Stanisław Przybyszewski.