Thiostrepton is a cyclic peptide antibiotic isolated from Streptomyces azureus. It targets a wide variety of gram-negative and gram-positive bacteria, especially those causing skin infections. It has been used as a marker for selection of recombinant Streptomyces cultures. Additionally, thiostrepton has been shown to inhibit FOXM1, a gene commonly overexpressed in cancer cell lines, thus inhibiting cancer cell growth.

Thiostrepton functions by binding elongation factor G (EF-G) and interfering with ribosomal GTPase activity, ultimately inhibiting protein synthesis.