The genus name Gloeobacter with the single (= type) species Gloeobacter violaceus (Cyanophyta, Cyanoprokaryota, Cyanobacteria) was described by Rippka, Waterbury et Cohen-Bazire (Arch. Microbiol. 100: 419-436, 1974). However, this is not a validly published name and so it currently has no standing under the botanical International Code of Nomenclature (ICN, Mc Neil et al. 2012) or the International Code of Nomenclature of Prokaryotes (ICNB/ICNP, Lapage et al. 1992). The lack of valid publication of the genus name causes many problems in the taxonomy of this phylogenetically and experimentally important cyanophyte/cyanobacterium. The lack of thylakoids, a feature unique among all known cyanobacteria, as well as the phylogenetic position of the representative of this genus, warrant valid publication of this generic name. The type strain was deposited in the collection PCC in Paris under the number PCC 7421 and later introduced into numerous other strain collections; however, the dried specimens were not yet conserved. The type strain is cited as holotype in Castenholz (Bergey's Manual, 2001). We here propose validation of the names Gloeobacter Rippka et al. 1974, gen. nov (type: Gloeobacter violaceus) and Gloeobacter violaceus Rippka et al. 1974, sp. nov., utilising the description by Rippka et al. reproduced here, and supported by the exsiccate BRNM No. HY 2366 (under the rules of the botanical Code of Nomenclature - ICN), using exsiccate from the type strain 7421 (PCC 7421T = ATCC 29082T).