Hans Joachim Wiehler (8 July 1930 in Klettendorf – 2003) was a German botanist who specialized in the plant family Gesneriaceae.
Wiehler tended to be a taxonomic "splitter" but many of his generic rearrangements have found acceptance: the segregation of Gasteranthus from Besleria, of Alsobia, Chrysothemis, Nautilocalyx, and Paradrymonia from Episcia, and of Moussonia from Kohleria, have all withstood the tests of recent molecular phylogenies.
However, most gesneriad specialists have not accepted his segregation of Bucinellina, Dalbergaria, Pentadenia, and Trichantha from Columnea, and his new genus Parakohleria has been synonymized under Pearcea.
His rare instances of taxonomic "lumping" have not been as widely accepted; Gloxinia sensu Wiehler is a polyphyletic assemblage, recently dismembered, and no other botanists have accepted his synonymy of Rhytidophyllum and Pheidonocarpa under Gesneria.
He has named the nothogenus ×Koellikohleria Wiehler (family Gesneriaceae) in Baileya, 16: 30 (1968).