The present disclosure relates to antibody-drug conjugates (ADCs) wherein one or more active agents are conjugated to an anti-B7-H3 antibody through a linker. The linker may comprise a unit that covalently links active agents to the antibody. The disclosure further relates to monoclonal antibodies and antigen binding fragments, variants, multimeric versions, or bispecifics thereof that specifically bind B7-H3, as well as methods of making and using these anti-B7-H3 antibodies and antigen-binding fragments thereof in a variety of therapeutic, diagnostic and prophylactic indications