Antibody–drug conjugates (ADCs) are immunoconjugates comprised of a monoclonal antibody tethered to a cytotoxic drug (known as the payload) via a chemical linker. The ADC is designed to selectively deliver the ultratoxic payload directly to the target cancer cells. To date, five ADCs have received market approval and over 100 are being investigated in various stages of clinical development. In this Therapeutics paper, we review recent clinical experience with the approved ADCs and other promising late-stage candidates on the horizon, following an overview of the biology and chemistry of ADCs and how the individual components of an ADC (antibody [or target], linker and conjugation chemistry, and cytotoxic payload) influence its activity. We briefly discuss opportunities for enhancing ADC efficacy, drug resistance, and future perspectives for this novel antibody-based molecular platform, which has great potential to make a paradigm shift in cancer chemotherapy.