Rifampicin (rifampin) is a semi-synthetic rifamycin antibiotic and one of the most important first-line drugs for the treatment of tuberculosis and leprosy. Structurally, it is an ansamycin in which a naphthohydroquinone chromophore is spanned by a long aliphatic ansa bridge, and its 3-(4-methylpiperazinyl) iminomethyl side chain confers oral activity. Rifampicin binds to the β-subunit of bacterial DNA-dependent RNA polymerase and sterically blocks the elongating RNA transcript, producing bactericidal and sterilising activity against both actively replicating and semi-dormant Mycobacterium tuberculosis. Owing to its high oral bioavailability and excellent tissue penetration, it is also used for meningococcal and Haemophilus influenzae type b chemoprophylaxis, implant-associated staphylococcal infections, brucellosis, non-tuberculous mycobacterial infections and Rhodococcus equi infection in foals. Its clinical use is limited by hepatotoxicity, potent induction of cytochrome P450 enzymes and drug transporters, and the rapid selection of resistance when used as monotherapy. Resistance arises mainly from mutations in the 81-bp rifampicin resistancedetermining region of the rpoB gene, and rifampicin resistance is now the defining marker of multidrug-resistant tuberculosis. This review summarises the history, chemistry, mechanism of action, pharmacokinetics, formulations, clinical applications, safety, resistance and environmental impact of rifampicin, and outlines the scope for future research, including high-dose regimens, shortened rifamycin-based therapy, nanocarrier delivery systems and remediation of rifampicin residues in the environment.