The school was founded in 1830 by the Faithful Companions of Jesus, or more specifically, their founder, Marie-Madeleine d'Houët. Just months after the school's opening, Marie later realised she could not keep running the school and passed the role of headteacher to Julie Guillemet, a friend of hers and FCJsister.
It was at first an industrial school financed by charitable appeals. The school then progressed to being a convent boarding school and then to a selective non-fee paying grammar school known as St. Aloysius.
The school then became a comprehensive in 1974 with the merger of St. Aloysius with St. Vincent's Schools which was run by the Sisters of Charity. The name Maria Fidelis was chosen by the Sisters meaning Mary Most Faithful.
Maria Fidelis today stands on Drummond Crescent in the Somers Town area of Camden, near Euston.
Since September 2013 (2013-09), the school admits boys as well as girls, in co-education.
Current Building
The High Speed 2 rail network's planned route was to go through North Gower Street, the location of the school's previous building. This meant the school was required to move locations to Drummond Crescent, nearby to Euston Road. Work began on the site in 2017 (2017) and the school started moving in 2018 (2018), before its official opening in September 2019 (2019-09).