Wikipedia
Shahbanu (in - Šahbānū) means "The Lady Shah" in Persian.
Upon assuming the title in 1967, Farah Pahlavi, the third wife of Mohammad Reza Pahlavi, was the first Shahbanu to be crowned in Iran since the Muslim conquest of Persia in the 7th century. The two Sassanian Empresses, Purandokht and Azarmidokht, c. 630, were the last two that carried the title before Farah Pahlavi.
The Sasanian title for Shahbanu was bâmbişnân bâmbişn, meaning the Queen of Queens, borne by the monarch's principal wife, to distinguish her from the other queens in the royal household.
Farah Pahlavi sometimes continues to be referred to as Shahbanu (or Empress), as is customarily done internationally for titleholders associated with abolished monarchies, but the title is no longer valid in Iran.
According to pre-revolutionary rules, Yasmine Pahlavi, Crown Princess of Iran, would currently hold this title.