Faecalibacterium is a genus of bacteria. Its sole known species, Faecalibacterium prausnitzii is a Gram-positive, mesophilic, rod-shaped, anaerobic and is one of the most abundant and important commensal bacteria of the human gut microbiota. Faecalibacterium prausnitzii is an extremely oxygen sensitive; EOS bacterium and is difficult to cultivate even in anaerobic conditions and widely distributed in the Gastrointestinal Tract; GIT of other mammals such pigs, mice and calves as well as poultry, and the insect cockroach. Changes in the abundance of fecal Clostridium leptum group, and in particular Faecalibacterium prausnitzii, have been extensively described in different human intestinal and metabolic diseases. Faecalibacterium prausnitzii is a butyrate producer and has demonstrated anti-inflammatory effects in vitro and in vivo using a mouse colitis model making it a key member of the microbiota that may contribute to intestinal homeostasis. Thus, modulation of Faecalibacterium prausnitzii abundance, for example using prebiotics and/or probiotics and/or formulations that permit survival through the upper part of the intestinal tract might have prophylactic or therapeutic applications in human health.