Pyocyanin is a blue-green pigment produced by the bacterium Pseudomonas aeruginosa. Its synonyms include methyl pyocyanin, phenazine-1-carboxylic acid, and 1-hydroxyphenazine. Pyocyanin is known for its cytotoxic and proinflammatory properties, and plays a role in P. aeruginosa virulence. Other related compounds produced by the bacterium include pyoverdine, pyorubrin, and pyomelanin. Pyoverdine is a fluorescent siderophore, while pyorubrin and pyomelanin are red and brown pigments, respectively. These compounds also contribute to the pathogenicity of P. aeruginosa by promoting biofilm formation, iron acquisition, and immune system evasion. Understanding the production and function of these compounds may aid in the development of new antimicrobial strategies.