Murtagh, 43, is widely regarded as one of the greatest riders of the modern era and partnered over 100 top-level winners at home and abroad during a stellar career.
In May of last year Murtagh took out his training licence, taking over the reins from Tommy Carmody at Fox Covert Stables in County Kildare.
While he enjoyed a fantastic campaign in what turned out to be his final season as a jockey, riding five Group One winners, he feels the time is now right to bring his illustrious riding career to an end.
Murtagh said: “The training side of things is getting bigger all the time and I wasn’t happy giving the riding 50 per cent and the training 50 per cent. It’s the right time to call it a day with the riding and put everything into the training side of things.”
Murtagh was successful in each of the five Irish Classics at least once, riding four Irish Derby winners and six Irish Oaks winners, including last year’s French-trained Oaks heroine Chicquita.
He also rode three winners of the Epsom Derby in Sinndar (2000), High Chaparral (2002) and Motivator and was successful in the 2,000 Guineas twice, aboard the brilliant Rock Of Gibraltar (2002) and Henrythe- navigator (2008).
Murtagh’s other British Classic victory came with a brilliant front-running ride aboard 2011 Oaks scorer Dancing Rain.
The jockey also had a great affinity with Royal Ascot, taking the leading rider award at the summer showpiece meeting for a fifth time last year.
He was stable jockey to O’Brien’s powerful Ballydoyle operation between 2008 and 2010, riding such greats as Henrythenavigator, Duke Of Marmalade and incredible four-time Gold Cup hero Yeats.
O’Brien said: “Johnny was a wonderful rider and we had great years together when he rode for us. He will be a great trainer and we would like to wish him, Orla [Murtagh’s wife and all the family every success in the future.”
Dettori paid tribute to his friend and former colleague, saying: “Johnny is probably one of the best judges of pace I’ve ever come across and one of the most hard working and talented jockeys I’ve ever ridden against. I’m genuinely upset that he will no longer be in the weighing room when I go in there.”