Necrotizing fasciitis (NF), commonly known as flesh-eating disease or flesh-eating bacteria syndrome, is a rare infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the fascial plane within the subcutaneous tissue.

Necrotizing fasciitis is a quickly progressing and severe disease of sudden onset and is usually treated immediately with high doses of intravenous antibiotics.

Type I describes a polymicrobial infection, whereas Type II describes a monomicrobial infection. Many types of bacteria can cause necrotizing fasciitis (e.g., Group A streptococcus (Streptococcus pyogenes), Staphylococcus aureus, Vibrio vulnificus, Clostridium perfringens, Bacteroides fragilis, Aeromonas hydrophila). Such infections are more likely to occur in people with compromised immune systems.