1809 in science

The year 1809 in science and technology involved some significant events, listed below.

Astronomy

Carl Friedrich Gauss publishes in Hamburg, introducing the Gaussian gravitational constant and containing an influential treatment of the least squares method.
S. D. Poisson publishes and in the Journal of the École Polytechnique, extending Lagrange's theory of planetary orbits.

Jean-Baptiste Lamarck publishes Philosophie Zoologique, outlining his theory of evolution.
Johann Heinrich Friedrich Link first describes Penicillium.

William Maclure publishes the first geological map of the United States with accompanying memoir.

December 25 – American physician Ephraim McDowell performs the world's first ovariotomy, the removal of an ovarian tumor.
Philippe Pinel publishes accounts of what would later be regarded as schizophrenia.

February 11 – Robert Fulton patents the steamboat in the United States.
May 5 – Mary Kies becomes one of the first women granted a U.S. patent, for a technique of weaving straw hats with silk and thread.
Samuel Thomas von Sömmerring invents a water voltameter electrical telegraph.

January 4 – Louis Braille (died 1852), French inventor.
January 6 – Marie Durocher (died 1893), Brazilian physician.
February 12 – Charles Darwin (died 1882), English naturalist.
February 15 – Cyrus McCormick (died 1884), American inventor.
February 21 – Carl Ernst Bock (died 1874), German physician and anatomist.
April 7 – James Glaisher (died 1903), English meteorologist and balloonist.
April 15 – Hermann Grassmann (died 1877), German mathematician.
April 20 – James David Forbes (died 1868), Scottish physicist, glaciologist and seismologist.
August 29 – Oliver Wendell Holmes Sr. (died 1894), American physician and writer.
November 22 – Bénédict Morel (died 1873), French psychiatrist.
Date unknown – William Lobb (died 1864), English plant collector.