However, he has previously spoken of wanting "a life outside ballet" and even expressed an ambition to open a tattoo parlour.
Sources told The Daily Telegraph that the dancer has told colleagues that he doesn't "want to go on dancing".
The Evening Standard
His mother Halina told the Standard she had taken a call in the middle of the night from her son, adding: "I would like to know very much what he is planning to do next.
"I know Sergei is a talented young man, he must know what he is doing. Believe me, he will never be lost in this world. If he made up his mind to do this, he must have thought it over very deeply indeed. He did not tell me the reason for it or what he is going to do next. He just said he was leaving."
On Friday Polunin is due to dance in Men in Motion, a programme at Sadler's Wells focusing on male dancers.
He was due to take the lead in The Dream at the Royal Ballet next week. The role is now likely to be danced by Steven McRae.