Librarians will generally require a master's degree in library science, also called an MLS. This degree is most often requested in positions located in special, academic, and public libraries. Licensing requirements vary from country-to-country and state-to-state, with each having its own minimum requirement. Some institutions also require a Librarian Certification.
Librarians in large universities will often hold a doctoral degree in library and information science, often participating in continuing eduction and library training programs. This helps librarians remain up-to-date on the best resources they can offer to their users.