Mollisonia is an extinct genus of Cambrian arthropod, noteworthy for being among the first identified with the mouth-legs known as Chelicerae, most famously a trait of arachnids like spiders, and therefore possibly among (or ancestral to) the first chelicerates. Species are known from the Burgess Shale, Langston Formation, and Wheeler Shale of North America, as well as the Chengjiang Biota of China. Twenty-one specimens of Mollisonia are known from the Greater Phyllopod bed, where they comprise less than 0.1% of the community. Remains possibly attributable to the genus are also known from the Ordovician Fezouata Formation of Morocco and Bøggild Fjord Formation in Greenland. An observation published in 2019 suggests this genus is a basal chelicerate, closer to crown group Chelicerata than members of Habeliida. It is suggested to be closely related to Corcorania, Urokodia (formerly ), and Thelxiope, which together form the clade Mollisoniida.