Polyketide synthases (PKSs) are a class of large, multi-functional enzymes that are responsible for the biosynthesis of polyketide compounds in various organisms, including bacteria, fungi, and plants. Polyketides are a diverse group of natural products that exhibit a wide range of biological activities, including antibiotic, anti-tumor, and anti-inflammatory properties. PKSs are divided into three main types: type I, type II, and type III. Type I PKSs are typically found in bacteria and fungi and are modular in structure, with each module catalyzing a specific step in the polyketide synthesis pathway. Type II PKSs are often found in bacteria and are composed of separate discrete enzymes that work together to synthesize polyketides. Type III PKSs are found in plants and are typically involved in the synthesis of pigments and defense compounds. Studies on polyketide synthases have provided valuable insights into the biosynthesis of polyketides and have led to the discovery of novel compounds with important medicinal and biotechnological applications. Researchers continue to study PKSs in order to better understand their function, optimize their production, and engineer them to produce new and improved polyketide compounds.