Mt. Lebanon is a home rule municipality, formerly a township, in Allegheny County, Pennsylvania, United States. The population was 33,137 at the 2010 census. An affluent suburb of nearby Pittsburgh, Mt. Lebanon is well known locally and nationally for its excellent school district. Mt. Lebanon High School is one of only 24 non-Private secondary schools in the United States (and the only non-Private school in Pennsylvania) that is a member of the prestigious Cum Laude Society.