Karl Friedrich Wilhelm Wallroth was a German botanist. His name is abbreviated Wallr. as a taxon authority.
He attended classes in medicine and botany at the University of Halle, afterwards continuing his studies in Göttingen, where he was a pupil of botanist Heinrich Adolf Schrader. In 1816 he obtained his medical doctorate at the University of Göttingen. In 1822 he was appointed district physician to the city of Nordhausen, where along with his duties as a doctor, he performed botanical research.
Among his writings were a treatise on cryptogams native to Germany, Flora Cryptogamica Germaniae, and a study on the biology of lichens, titled Naturgeschichte der Flechten. He is credited for introducing the terms "homoiomerous" and "heteromerous" to explain two distinct forms of lichen thallus.