This document presents the ligand-binders ontology developed to standardize information about protein binders and their targets. The ontology defines concepts like binders, targets, experiments, and their properties and relationships. It represents key concepts through classes and subclasses, and defines class properties to describe concepts. The ontology aims to provide a standardized vocabulary and enable reasoning about protein binder technologies. It was developed based on domain expertise and minimal information needed to describe binder-target pairs.