Otto Wilhelm Sonder (18 June 1812, Bad Oldesloe – 21 November 1881) was a German botanist and pharmacist.

[1] A native of Holstein, Sonder studied at Kiel University, where he sat pharmaceutical examinations in 1835, before becoming the proprietor of a pharmacy in Hamburg from 1841 to 1878.

[2] In 1846 he received an honorary doctorate from the University of Königsberg and was elected a member of the German National Academy of Sciences Leopoldina for his contribution to the field of botany.

[4] He amassed an extensive botanical collection that contained hundreds of thousands of herbarium specimens representing all major plant groups and spanning all parts of the globe.

Between late 1874 and early 1875, Sonder worked his way through the entire collection, sorting material and remounting specimens where needed.