Donnacha O'Brien (born 22 July 1998) is an Irish racehorse trainer and former jockey who competed in Flat racing.
Donnacha O'Brien rode his first winner on Quartz, trained by his father, at Dundalk Stadium in September 2014, and gained his first Group 1 victory when he rode Intricately to win the 2016 Moyglare Stud Stakes.
Intricately was bred by his mother, Anne Marie, and trained by his brother.
O'Brien was Irish flat racing champion apprentice jockey in 2016 and Irish flat racing Champion Jockey for the first time in 2018.
This Irish horse racing biographical article is a stub.