Franz Carl Mertens
（重定向自Mert.）
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Franz Carl Mertens (3 April 1764 – 19 June 1831) was a German botanist who was a native of Bielefeld. He specialized in the field of phycology.
Mertens studied theology and languages at the University of Halle, and after graduation taught classes at Bremen Polytechnic College. In his spare time he studied botany, and through a mutual friend met German botanist Albrecht Wilhelm Roth (1757–1834). With Roth, he took scientific expeditions throughout Europe, including Scandinavia.