His Holiness is a style and form of address (in the variant form Your Holiness) for some supreme religious leaders. The title is most notably used the Pope, Oriental Orthodox Patriarchs, and Dalai Lama.
His Holiness (Latin: Sanctitas) is the official style used to address the Roman Catholic Pope and Oriental Orthodox Patriarchs. In the Eastern Orthodox Church, the Ecumenical Patriarch of Constantinople has the title of His All-Holiness (abbreviation HAH).
The term is sometimes abbreviated to "HH" or "H.H." when confusion with "His/Her Highness" is unlikely. The associated form of address is "Your Holiness".
Later, it is also used for certain other Eastern Patriarchs, notably those who head a church or rite which recognizes neither Rome's nor Constantinople's primacy.
The English language honorific "His Holiness", and as female version "Her Holiness", has commonly been used for religious leaders from other traditions, including Buddhism (for figures such as the Dalai Lama, the Karmapa, and the Je Khenpo in Bhutan), Shinto in Ahmadiyya Islam for the Caliph and in Dawoodi Bohra sect of Ismaili Shia for esteemed office of Da'i Al-Mutlaq, Syedna.