Mount St. Michael is an all-girls voluntary secondary school, under the trusteeship of the Ceist, situated on the outskirts of Claremorris in County Mayo, Connacht, Ireland, and was originally part of the estate of Denis Browne (Landlord). It was founded in 1906 and began as a 'Secondary Top' in 1924. It developed into a full secondary school in 1940.
Until 2000 the school accommodated both residential and day pupils. Boarders were first admitted in 1906 and the annual intake numbered 15 between 1906 - 1940. This number increased to 90 until 1996 when the phasing out of the Boarding School was begun. The current student population numbers about 450.
In 1977 a Parents' Council, affiliated to the National Catholic Secondary Parents' Associations (CPSA) was formed.
In 1987 a Board of Management was set up, comprising representatives of trustees, teachers and parents. In 1990 a Lay principal was appointed.
Since 1977 the school has a Students' Council whose members are elected by students and staff from the Leaving Certificate student group.
Mount St. Michael operates a 6-year cycle since 1976 when Transition year was first introduced as a Pilot project by the Department of Education.