What is the title of a Zoroastrian high priest?

The title of a Zoroastrian high priest is dastur.

A dastur is a senior Zoroastrian cleric with authority in religious matters. The title ranks above offices such as mobad and herbad, although exact clerical structures and usage can vary between Zoroastrian communities.

The word is especially associated with the Parsis of India. In that context, it became a prominent honorific for leading priests and holders of established religious seats. The first person traditionally given the title was Meherji Rana, who visited the court of Mughal emperor Akbar in the late sixteenth century.

Dastur is not interchangeable with guru, imam, or rabbi: those titles belong to different religious traditions. A mobad is also a Zoroastrian priest, but dastur denotes the higher rank in the usage described here. The word has additionally been used in Persianate contexts for a minister or government counselor, so its meaning depends on context.