Brendan Michael O'Brien (born September 28, 1943) is a Canadian prelate of the Roman Catholic Church.

In 1971 he went to Rome, where he studied at the Pontifical Lateran University's Accademia Alfonsianum, from which he obtained a doctorate in moral theology.

O'Brien, upon his return to Canada in 1975, taught at his alma mater of St. Paul University and served as pastor of an Ottawa parish.

He received his episcopal consecration on the following June 29 from Archbishop Joseph-Aurèle Plourde, with Bishops John Beahen and Gilles Bélisle serving as co-consecrators.

Pope Benedict XVI, on June 3, 2007, named O'Brien to succeed the late Anthony G. Meagher as Archbishop of Kingston.