As Alistair says, “Ballet Master Associated with the Direction of Dance” is how Patrice Bart appears in the production credits of the film La Danse, featuring the Paris Opera Ballet, in the “Great Performances” website.
Brigitte Lefèvre, in the same list, is called “Director of Dance”.

However, these titles cannot be regarded as definitive, since in the company’s own website, English version, he is called “ballet-master, associated to the company director”, and Mme Lefèvre is duly called “company director”.
http://www.operadeparis.fr/cns11/live/onp/L_Opera/le_Ballet/...

Their titles in French are respectively “maître de ballet, associé à la direction de la danse” and “directrice de la danse”.
http://www.operadeparis.fr/cns11/live/onp/L_Opera/le_Ballet/...

It seems to me that both M. Bart’s titles in the above sources must be regarded as bad translations from the French. At least in the first we have “associated with” instead of “associated to”, but “associated with” is not an expression one would normally use for “associé à” in this context. You can have an associate director or an assistant director, but not a ballet master “associated with” (let alone “to”) the director. I would also say “Direction of Dance” is a bizarre calque of “direction de la danse”. Normally “direction of dance” would mean the direction in which one is dancing. In the Opera de Paris site we have “director” here rather than “direction”, which is a step in the right direction (if you’ll pardon the pun).

So I would recommend using the kind of terminology customary in British and American companies. There are various options.

The most usual English term for the position Brigitte Lefèvre (a distinguished ex-ballerina) occupies in Paris is Artistic Director:
“The head of a ballet company is called the artistic director. He or she is usually a retired dancer, and often he choreographs some of the company's productions himself. In a large company he will have one or more assistants. Day to day coaching of the dancers is the responsibility of one or more ballet masters and ballet mistresses.”
http://en.wikipedia.org/wiki/Ballet_company
Historically, it used to be called the First Ballet Master (ballet terminology is largely French in origin:
“Especially during the early centuries of ballet troupes and ballet companies from the 18th century until the early 20th century, the position of First Ballet master, referred to traditionally as the Premier Maître de ballet en Chef or more simply as the Maître de ballet, was the undisputed head of the company who acted as chief choreographer and Artistic Director.”
http://en.wikipedia.org/wiki/Ballet_master

At the Royal Ballet, Monica Mason is simply called Director
At the English National Ballet, Wayne Eagling is Artistic Director (there is also an overall Director, a general administrator).
Los Angeles Ballet has two Artistic Directors, Thordal Christensen and Colleen Neary.
At New York City Ballet, Peter Martins retains the old-fashioned title of “Ballet Master in Chief”, but he is also referred to as the Artistic Director.
http://www.nycballet.com/company/personnel/artistic/martins....

So I recommend Artistic Director. An alternative, if you want to stay closer to the original term, could be “Director of Dance”. As for “adjunto a” / “associé a”, which is not part of the question, I would put “Ballet Master, assistant to the Artistic Director”, or if you like, following common Anglo-American usage, simply “Assistant Artistic Director”.