From The Encyclopedia of Arda: On 'Istari'
Quote:
Istari
The order of Wizards, the Maiar who came to Middle-earth after the first millennium of the Third Age. Of these, five came to the northwestern regions; Saruman, Gandalf, Radagast, Alatar and Pallando.
|
The wording suggests that there may have been more, but I think Tolkien might have mentioned it if there were more...