Friedrich Sigmund Merkel (5 April 1845 – 28 May 1919) was a leading German anatomist and histopathologist of the late 19th century. In 1875, he provided the first full description of Tastzellen (touch cells), which occur in the skin of all vertebrates. They were subsequently given the eponym "Merkel cells" in 1878 by Robert Bonnet (1851–1921).

Merkel was a native of Nürnberg. In 1869 he earned his medical doctorate from the University of Erlangen, becoming habilitated in the field of anatomy during the following year. He was a professor at the Universities of Rostock (from 1872), Königsberg (from 1883) and Göttingen (from 1885). At Göttingen, he worked under Jacob Henle and married Henle's daughter Anne. He published a multivolume textbook on human anatomy and originated the color scheme used by most anatomy texts today: red for arteries, blue for veins, and yellow for nerves. He introduced xylene as a clearing agent in histology, and it is still used today Two of his better known assistants were Dietrich Barfurth (1849-1927) and Hermann Kuhnt (1850-1925).

The term "Merkel's spur" is synonymous with the femoral calcar.