About 95% of fatal mushroom poisonings worldwide are caused by amatoxins and phallotoxins mostly produced by species of Amanita, Galerina, and Lepiota. The genus Lepiota is supposed to include a high number of species producing amatoxins. In this study, we investigated 16 species of Lepiota based on 48 recently collected specimens for the presence of amatoxins by liquid chromatography coupled to a diode-array detector and mass spectrometry (UHPLC-QTOF-MS/MS). By comparing the retention times, UV absorptions, and diagnostic MS fragment ions with data obtained from the benchmark species Amanita phalloides, we detected α-amanitin and γ-amanitin in Lepiota subincarnata, α-amanitin and amaninamide in Lepiota brunneoincarnata, and β-amanitin and α-amanitin in Lepiota elaiophylla. Phallotoxins have not been detected any of these species. Two possibly undescribed amatoxin derivatives were found in Lepiota boudieri and L. elaiophylla, as well as one further non-amatoxin compound in one specimen of L. cf. boudieri. These compounds might be used to differentiate L. elaiophylla from L. xanthophylla and species within the L. boudieri species complex. No amatoxins were detected in L. aspera, L. castanea, L. clypeolaria, L. cristata, L. erminea, L. felina, L. fuscovinacea, L. lilacea, L. magnispora, L. oreadiformis, L. pseudolilacea, L. sp. (SeSa 5), and L. subalba. By combining the occurrence data of amatoxins with a phylogenetic analysis, a monophyletic group of amatoxin containing species of Lepiota is evident. These chemotaxonomic results highlight the relevance of systematic relationships for the occurrence of amatoxins and expand our knowledge about the toxicity of species of Lepiota.