The present invention relates to monoclonal antibodies and antigen-binding portions thereof that specifically bind to a filovirus (e.g., Marburg virus (MARV)), including antibodies that cross-react with at least two filoviruses. Such antibodies are useful for the prevention and treatment of filovirus infection. The invention also provides pharmaceutical compositions comprising the MARV-binding antibodies, nucleic acid molecules encoding these polypeptides and methods of making these molecules.