Bettina von Arnim was closely related to the German writers Clemens Brentano and Achim von Arnim: the first was her brother, the second her husband. Her daughter Gisela von Arnim became a prominent writer as well.

Bettina was born in Frankfurt on Main, Germany, on April 4, 1785, into the large family of an Italian merchant. Her grandmother, Sophie von La Roche, was a novelist and her brother was Clemens Brentano, the great poet known for his lyric poems, libretto and singspiel. He was a mentor and protector to her, and influenced her to read poetry of the time, especially Goethe.

After being educated at a convent school in Fritzlar, she lived for a while with her grandmother at Offenbach am Main, and from 1803 to 1806 with her brother-in-law, Friedrich von Savigny, the famous jurist, at Marburg. In 1807 she made at Weimar the acquaintance of Goethe, for whom she entertained a significant passion, which the poet, although entering into correspondence with her, did not requite, but only regarded as a harmless fancy. Their friendship came to an abrupt end in 1811, owing to Bettina's behaviour with Goethe's wife.

In 1811 she married Achim von Arnim, the renowned Romantic poet. They settled near Berlin and had seven children. Achim died in 1831, but Bettina maintained an active public life. Her passion for Goethe revived, and in 1835, after lengthy discussions with the writer and landscape gardener Hermann von Pückler-Muskau she published her book, Goethes Briefwechsel mit einem Kinde, which purported to be a correspondence between herself and the poet. She continued to write, inspire and publish until January 20, 1859, when she died surrounded by her children.

From 1991 until 31 December 2001, her portrait was printed on the German 5-DM bill.

The years of 1806-08, she was integral to gathering the folk songs for Des Knaben Wunderhorn, the collaborative work of her brother and her future husband, Achim von Arnim. This piece became a touchstone of the Romantic musical and poetic style. From 1808 to 1809 she studied voice, composition and piano in Munich under Peter von Winter and Sebastian Bopp. She published her first song under the pseudonym Beans Beor which she occasionally used later as well. Bettina sang briefly in the Berliner Singakademie and composed settings of Hellenistic poems by Amalie von Helvig.

It was thought that she had stopped composing due to her domestic duties after her 1811 marriage, but several more art songs have been recovered and have been published in Werke und Briefe. Another notable fact is that she was the first composer to set the poet Hölderlin’s work to song.

She was a muse to the progressives of Prussia. She was linked to the socialist movement and was an advocate for the oppressed Jewish community. She published two politically dissident works but she evaded chastisement because of her friendship with the King of Prussia.

After the 1831 death of her husband, Bettina continued her dedication to the creative community. She published a collection of seven songs as a public sign of support for Prussian Music Director, Gaspare Spontini, who was under a great deal of duress.

The failed 1847 German settlement of Bettina in Texas was named by its progressive, idealistic founders for Bettina von Arnim. It was located near the join of Elm Creek and the Llano River, and lasted only a year, disbanding in 1848. There is no trace of the Bettina community, other than the later prominence of two of its founders, Gustav Schleicher (later a U.S. congressman and namesake of Schleicher County) and Dr. Ferdinand Herff, who in 1854 became the first surgeon to use anesthesia in Texas.

Part of a design by her for a colossal statue of Goethe, executed in marble by the sculptor Karl Steinhauser (1813—1878), was in the museum at Weimar in 1911.