The bacterial order Chlamydiales includes only obligately intracellular bacteria that have a chlamydia-like developmental cycle of replication and at least 80% 16S rRNA or 23S rRNA gene sequence identity with other members of Chlamydiales.

Chlamydiales live in animals, insects, and protozoa.

Currently, the order Chlamydiales includes the families Chlamydiaceae, Simkaniaceae, and Waddliaceae, which have Gram-negative extracellular infectious bodies (EBs), and Parachlamydiaceae, which has variable Gram staining of EBs.

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[1] and National Center for Biotechnology Information (NCBI)[2] Simkaniaceae Waddliaceae Parachlamydiaceae Chlamydiaceae "Ca.

Amphritriteisimkania" {JACRBE01} Simkaniaceae Everett, Bush & Andersen 1999 "Rhabdochlamydiaceae" Corsaro et al. 2009 "Ca.s Rubidus" {Parachlamydiaceae_B} Waddliaceae Rurangirwa et al. 1999 "Criblamydiaceae" Thomas, Casson & Greub 2006 Parachlamydiaceae Everett, Bush & Andersen 1999 Chlamydiaceae Rake 1957 This bacteria-related article is a stub.