Killian Brennan (born 31 January 1984) is an Irish retired footballer who played as a midfielder in the League of Ireland Premier Division.

Noted for his wing play and ability to fire in accurate crosses, Brennan was signed by Peterborough United in his teenage years.

He was signed by John Gill for Dublin City, however, less than a year later, newly appointed boss Roddy Collins' 'purge' of the club meant that Brennan was deemed surplus to requirements.

He continued his good form netting 5 times in May 2008 and this did not go unnoticed as he was awarded Soccer Writers' Association of Ireland Player of the month for May.

[3] He then scored again on 20 October as Bohs beat St. Patrick's Athletic to put them on top of the table and that's where they finished as Bohemians won their first ever back-to-back league wins.

[4] Despite winning the Setanta Sports Cup,[5] Bohemians had a disappointing 2010 season where the club lost their league title on goal difference and failed to make an impact in Europe where they made an embarrassing exit to Welsh side The New Saints.

[8] Brennan started off life at his new club brilliantly, getting the Man of the Match award in a 0–0 draw at home to Glentoran live on Setanta Sports.