AbstractSummary: This feature article describes the current knowledge on biosynthesis of polythioesters (PTEs), which are exclusively accumulated by microorganisms capable to synthesize the well‐known polyhydroxyalkanoates (PHAs). Two bacterial PTE biosynthesis systems are discussed, both are depending on the cultivation conditions and appropriate feeding regimes. The first system comprises the production of PTE copolymers by Ralstonia eutropha, and the second system has been established in recombinant Escherichia coli to produce PTE homopolymers. Furthermore, synthetic PTEs and other related sulfur containing biopoylmers are briefly summarized.General structural formula of PTEs accumulated as small granules in cells of metabolically engineered Escherichia coli.imageGeneral structural formula of PTEs accumulated as small granules in cells of metabolically engineered Escherichia coli.