[1] Although priority is given to those of the main Catholic tradition, as a Christian school, it is attended by students of other denominations and faiths.

In 1830, a year after the passing of Catholic Emancipation, priests from the Vincentian Community (Congregation of the Mission; CM) in Maynooth College obtained permission to open a day school under the patronage of the Archbishop of Dublin.

On 28 August 1835, St. Vincent's Ecclesiastical Seminary was opened in Castleknock, as a boarding school catering for just 47 boys.

The intended visit of the Queen to Castleknock was made known to the authorities of the school some days beforehand by the Rudolph Feilding, 9th Earl of Denbigh.

[9] Sporting facilities at the school include nine rugby pitches, one soccer pitch, a cricket crease with pavilion, table tennis room, state of the art tennis courts, a fully equipped weights room and an athletics track.

Throughout the mid-nineteenth century a game peculiar to Castleknock, known as stilts, was played by the entire student body on a gravel patch in grounds.

[12] 26 past men have represented Ireland at full international level, the most recent being Leinster Rugby's Devin Toner (class of 2004) who has been capped on seventy occasions.

Toner is one of two past men to have won the Heineken Cup (2009, 2011, 2012) with Denis Hurley of Munster Rugby lifting the trophy in 2008.

Past men James Leo Farrell and Michael Dunne were part of the British and Irish Lions touring squad to New Zealand and Australia.

The college has minor, junior, intermediate and senior athletics teams which compete for, and have won, the West Leinster Championship.

[13] Castleknock College competes in a variety of other sports including soccer, cricket, tennis, table-tennis, badminton, golf, swimming, show-jumping and volleyball.

Members are involved in helping the impoverished through a variety of means such as visiting local centres for people with special needs.

This development programme has enabled the construction of expanded education facilities and the provision of medical and food supplies.

In both 2007 (Alan Henry & Liam O'Connell) and 2008 (Adam Noonan & Killian Breen) the college won the Leinster Schools Senior Debating Championships.

[17] Past speakers at the Union Debate include former Attorney General Paul Gallagher, Eunan O'Halpin, Mick Quinn and Irish Times correspondent Patsy McGarry.

Former winners of the senior gold medal debates include the Taoiseach Liam Cosgrave, the Supreme Court Justice Anthony J. Hederman, Conor Gearty and Oisín Quinn.

The former is reputed to be the burial mound of Cumhal, father of Fionn mac Cumhaill, a legendary Irish warrior.

An archaeological dig of this hill carried out in June 2007 revealed the remains of four human skeletons probably dating from the early Christian period.

A state-of-the-art multi purpose sports and tennis ground was recently built, allowing for students and others to enjoy various activities.

The film stars Sophie Vavasseur in the title role, Pierce Brosnan as her father and Aidan Quinn, Julianna Margulies, Stephen Rea and Alan Bates as supporters to Doyle's case.

[30][31][32] Many notable figures have been guest speakers at the annual Business lunch such as the Irish rugby head coach Joe Schmidt and the Taoiseach Leo Varadkar.

The school's alumni and faculty include two Taoisigh,[36] one President of Ireland,[37] one Ceann Comhairle, several cabinet ministers,[38] two Supreme Court Justices,[39] five Attorneys General,[40] one Lord Chief Justice of England and Wales, three archbishops, one founding member of Fianna Fáil, the founder of the Green Party of Ireland,[41] one Lord Mayor of Dublin,[42] one Victoria Cross holder,[43] 26 Irish International rugby players and numerous notable figures in the world of arts, academia and business.

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