Cyclic peptides combine a number of favorable properties that make them attractive for drug development. Today, more than 40 therapeutics based on cyclic peptides are in use, and new, powerful technologies for their development suggest that this number could grow rapidly. In this review, we feature cyclic peptide drugs developed in the past, discuss the properties of this molecule class, describe technological advances, and discuss current challenges and opportunities for developing the next generation of cyclic peptide therapeutics. Cyclic peptides are fascinating molecules abundantly found in nature and exploited as molecular format for drug development as well as other applications, ranging from research tools to food additives. Advances in peptide technologies made over many years through improved methods for synthesis and drug development have resulted in a steady stream of new drugs, with an average of around one cyclic peptide drug approved per year. Powerful technologies for screening random peptide libraries, and de novo generating ligands, have enabled the development of cyclic peptide drugs independent of naturally derived molecules and now offer virtually unlimited development opportunities. In this review, we feature therapeutically relevant cyclic peptides derived from nature and discuss the unique properties of cyclic peptides, the enormous technological advances in peptide ligand development in recent years, and current challenges and opportunities for developing cyclic peptides that address unmet medical needs.