Helmina von Chézy (26 January 1783 – 28 February 1856), née Wilhelmine Christiane von Klencke, was a German journalist, poet and playwright. She is known for writing the libretto for Carl Maria von Weber's opera Euryanthe (1823) and the play Rosamunde, for which Franz Schubert composed incidental music.
Helmina was born in Berlin, the daughter of Prussian officer Carl Friedrich von Klencke and his wife Caroline Louise von Klencke (1754–1802), daughter of Anna Louisa Karsch and herself a poet. The marriage of her parents had already broken up at her birth and she was partly raised by her grandmother. She debuted as a writer at the age of 14.
Married the first time in 1799, she divorced the next year and upon the death of her mother moved to Paris, where she worked as a correspondent for several German papers. From 1803 to 1807 she edited her own Französische Miszellen ("French Miscellanea") journal, commenting on political issues, which earned her trouble with the ubiquitous censors.
In Paris she befriended Friedrich Schlegel's wife Dorothea, who introduced her to the French orientalist Antoine-Léonard de Chézy. In 1805 they married and Helmina subsequently gave birth to two sons: the later author Wilhelm Theodor von Chézy (1806–1865) and Max von Chézy (1808–1846), who became a painter. In 1810, together with Adelbert von Chamisso, she translated several of Friedrich Schlegel's lectures from French into German. They had a short romantic fling, followed by another extramarital affair of Helmina with the Austrian orientalist Joseph von Hammer-Purgstall, probably the father of another son who died shortly after his birth in 1811.