Custodian of the Two Holy Mosques (abbreviation CTHM; Arabic: خَادِمُ ٱلْحَرَمَيْنِ ٱلشَّرِيفَيْنِ, romanized: Khādim al-Ḥaramayn aš-Šarīfayn, lit.

'Servant of the Two Noble Sanctuaries'), or Protector of the Two Holy Cities, is a royal style that has been used officially by the monarchs of Saudi Arabia since 1986.

The title was sometimes regarded to denote the de facto Caliph of Islam,[1] but it mainly refers to the ruler taking the responsibility of guarding and maintaining the two holiest mosques in Islam: Al-Haram Mosque (Arabic: اَلْمَسْجِدُ ٱلْحَرَامُ, romanized: Al-Masjid al-Ḥarām, "The Sacred Mosque") in Mecca and the Prophet's Mosque (Arabic: اَلْمَسْجِدُ ٱلنَّبَوِيُّ, romanized: Al-Masjid an-Nabawī) in Medina,[1][2] both of which are in the Hejazi region[3] of Saudi Arabia.

[5] After defeating the Mamluks and gaining control of the Mecca and Medina in 1517, the Ottoman sultan Selim I adopted the title.

[6][7][8] The first King of Saudi Arabia to assume the title was Faisal bin Abdul Aziz (1906–1975).