One of the greatest achievements of modern medicine is the development of antibiotics against life-threatening infections, but the emergence of multidrug-resistant (MDR) gram negative bacteria has drastically narrowed down the therapeutic options against them. This limitation has led clinicians to reappraise the clinical application of polymyxins, an old class of cationic, cyclic polypeptide antibiotics. Polymyxins are active against selected gram-negative bacteria, including the Acinetobacter species, Pseudomonas aeruginosa, Klebsiella species, and Enterobacter species. In this article, we summarise the chemistry, pharmacokinetics, and pharmacodynamics of polymyxins and the latest understanding of their action against MDR pathogens.