The Rhizobiaceae are a family of proteobacteria, including many (but not all) species of rhizobia as well as plant parasites like Agrobacterium. Rhizobiaceae are, like all Proteobacteria, gram-negative. They are aerobic and the cells are usually rod-shaped. Many species of the Rhizobiaceae are diazotrophs, they are able to fix nitrogen and are symbiotic with plant roots.
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)  and National Center for Biotechnology Information (NCBI) and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project 
- ^ a b J.P. Euzéby. "Proteobacteria (scroll down for Rhizobiaceae)". List of Prokaryotic names with Standing in Nomenclature (LPSN) . http://www.bacterio.cict.fr/classifphyla.html#Proteobacteria. Retrieved 2012-05-02.
- ^ Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two: The Proteobacteria, Part C: The Alpha-, Beta-, Delta-, and Epsilonproteobacteria. New York, New York: Springer. ISBN 978-0-387-24145-6.
- ^ Sayers et al.. "Rhizobiaceae". National Center for Biotechnology Information (NCBI) taxonomy database . http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=82115&lvl=4&lin=f&keep=1&srchmode=1&unlock. Retrieved 2012-05-02.
- ^ All-Species Living Tree Project."16S rRNA-based LTP release 106 (full tree)". Silva Comprehensive Ribosomal RNA Database . http://www.arb-silva.de/fileadmin/silva_databases/living_tree/LTP_release_106/LTPs106_SSU_tree.pdf. Retrieved 2012-05-02.
- ^ a b c d e f These species were formerly classified in the genus Agrobacterium.
- ^ a b c d e f This is the type species for the genus.
- ^ Arthrobacter viscosus is currently classified in the Micrococcaceae. (See Arthrobacter.
- ^ a b c d e f Species found in the genera Aurantimonas, Aureimonas, Fulvimarina, and Martelella are all currently classified in the Aurantimonadaceaea.
- ^ a b c The species in the genus Aureimonas were formerly classified in the genus Aurantimonas.
- ^ Beijerinckia fluminensis is currently classified in the Beijerinckiaceae.
- ^ This includes Agrobacterium tumefaciens (Smith and Townsend 1907) Conn 1942.
- ^ Blastobacter capsulatus is currently classified in the Bradyrhizobiaceae.
- ^ a b c d e f g These species were formerly classified in the genus Sinorhizobium.