The absence of Faecalibacterium prausnitzii in human gut microbiota is associated with several dysbiotic diseases. F. prausnitzii can be thus considered as a biomarker of human health. It is now a major actor in novel preventive and curative strategies required to prevent and to treat gastrointestinal disorders and diseases. Here, we will present our most recent data on the mode of action, with a focus on the anti-inflammatory F. prausnitzii MAM (for Microbial Anti-inflammatory Molecule) protein. More recently, we have also tested F. prausnitzii i) in Sars-CoV2 and influenza virus and ii) immune-oncology preclinical models and we will present these results. All these results confirm the high potential of F. prausnitzii as a Live Biotherapeutics for several diseases and especially for inflammatory bowel disease (IBD). Given its strong links to IBD in humans, F. prausnitzii is being used for the first time in a clinical trial focused on Crohn’s Disease.