Chimpanzee monoclonal antibodies and antigen binding fragments including a .gamma.1-chain CDR3 region that bind hepatitis A virus (HAV) antigen are disclosed herein. The antibodies neutralize HAV. Also disclosed are methods for using these antibodies and antigen binding fragments in the detection of hepatitis A virus, the inhibition of infection of a subject with hepatitis A virus, and in screening for agents that affect HAV.