Iain Edward O'Brien (born 10 July 1976) is a former New Zealand cricketer, who played 22 Tests, 10 ODIs and 4 T20Is.

He enjoyed much success as a fast bowler for the Black Caps, with great performances against England in the UK, and against the West Indies cricket team at home, where he took his best Test figures of 6/75, in a spell of bowling regarded as one of the best in New Zealand.

[3] Against the Pakistan cricket team at home in December 2009, he has become well known for bowling New Zealand to victory by taking 3 wickets while suffering from a broken thumb.

In this same series, he took 6 wickets in the next game, including 4/66, dismissing the likes of Salman Butt, Imran Farhat and Misbah-ul-Haq.

The 2010 season was a frustrating one for O'Brien, he took 23 wickets at an average of 27.30 for Middlesex in division two of the County championship.