Frankie Dettori is to leave Godolphin after being retained rider to Sheikh Mohammed's operation for 18 years.
The Italian jockey rode nine English Classic winners for Godolphin and partnered the great Dubai Millennium to glory in the Dubai World Cup of 2000.
"We have had a tremendous association with Frankie over many years. He has achieved so much. However, Frankie is looking for a fresh challenge and we felt that the retainer was not really working, so this is the best way forward," said Godolphin racing manager Simon Crisford.
"We have had many great days together and we look forward to working with Frankie in the future and hopefully enjoying more success together.
"He remains a great friend - the difference next year will be that he will not be our retained jockey and will operate as a freelance instead," he told www.godolphin.com.
Dettori, who rode Godolphin's first Classic winner, Balanchine, in 1994 and has been associated with many of the stable's top horses since then, said: "I have had 18 wonderful years. Godolphin has been a major part of everything I have achieved in racing and I have loved every minute of it.
"I feel the time has come for a change. My position in the stable has changed a little bit and I need a new challenge.
"Sheikh Mohammed has been an unbelievable boss to me. He had the confidence to take me on board when I was young and we smashed every record together. I will be forever grateful to him for everything he has done for me and for my family."
Dettori, winner of 110 Group or Grade One races in the royal blue silks, thanked the many Godolphin staff who had helped him to achieve the success he has enjoyed with the stable. "The whole team have been fantastic - none of it would have been possible without them," he said.
Godolphin's retained riders in 2013 will be Mickael Barzalona and Silvestre de Sousa.