Abstract: Disclosed are monoclonal antibodies and antigen binding fragments that specifically bind epidermal growth factor receptor (EGFR) variant (v) III, conjugates thereof, and chimeric antigen receptors. Nucleic acid molecules encoding the heavy and light chain domains of the antibodies, and the chimeric antigen receptors (CARs), are also disclosed, as are host cells expressing the nucleic acid molecules. In addition, disclosed is the use of these monoclonal antibodies, antigen binding fragments, conjugates, and T cells expressing the CARs, such as for the treatment of a tumor expressing EGFRvIII. Also disclosed are methods for detecting a tumor that expresses EGFRvIII.