Multiple Group One-winning jockey Donnacha O'Brien has announced his retirement from riding and will become the latest member of his family in the training ranks.

The 21-year-old has been champion jockey in Ireland for the past two years and he bows out with 10 top-level wins to his name.

O'Brien's final Group One success came aboard Magical in the Champion Stakes at Ascot in October.

"After thinking about things for a while, I have decided to concentrate on training next year," O'Brien said on Twitter.

"Riding has been very good to me and I owe everything to the people around me.

"I want to give special thanks to the Magnier, Smith and Tabor families, along with my own family, for all their support.

"I look forward to training a small group of horses next year and will hopefully build from there."

O'Brien's father Aidan, a champion amateur rider, trains for Coolmore and has created many records during his career.

Donnacha's 26-year-old brother Joseph, also a champion rider before weight became a problem, trained the 2017 Melbourne Cup winner Rekindling and last month became the youngest person to train a Breeders' Cup winner.

Donnacha O'Brien rode his first winner aboard Quartz for his father at Dundalk in September 2014 when he was just 16, graduating to be champion apprentice in 2016 and riding out his claim in April 2017.

He chalked up his first century of winners last year in claiming the riders' title, and he finished this season on 111 to match Joseph in winning back-to-back championships.