M.Lib, also known as MLIS or Master of Library and Information Science, is a postgraduate degree program in the field of library and information science. It is designed for students who have already completed a B.Lib (Bachelor of Library and Information Science) or an equivalent degree. The program usually lasts 1 or 2 years, depending on the university or country, and focuses on advanced principles and techniques of managing libraries, archives, and digital information systems.