Arthrospira is a genus of free-floating filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-hand helix. It was originally proposed in 1892 and went through a period of disuse between 1932 and 1974 due to an error perpetuated by Geitler. It contained the cultivated species used for producing spirulina until 2019, when it was found that the sequence of the type species A. jenneri was only distantly related to the cultivated species with several established genera in between, causing a new genus Limnospira to be created for them.