The royal doors, holy doors, or beautiful gates are the central doors of the iconostasis in an Eastern Orthodox or Eastern Catholic church.
In Orthodox Churches, the sanctuary is separated from the nave by a wooden screen called the iconostasis. The iconostasis represents Christian continuity from the veil of the Temple in Jerusalem which separated the people from the Holy of Holies that housed the Ark of the Covenant. Normally, the iconostasis has three doors in it. The two single doors to the right and left are called "deacons' doors" or "angel doors" and they usually have on them icons of either sainted deacons (Saint Stephen, Saint Lawrence, etc.) or the Archangels Michael and Gabriel. These are the doors that the clergy will normally use when entering the altar. The central double doors are the "holy doors" (Slavonic: Svyatýa Vratá), which are considered to be most sacred, and may only be entered at certain sacred moments during the services, and only by ordained clergy (deacons, priests, bishops).
The term Royal Doors (Slavonic: Tsárskiya Vratá) is commonly used to describe the Holy Doors, because Christ passes through these gates during the Great Entrance at the Divine Liturgy (and most especially during the Liturgy of the Presanctified Gifts). More properly, however, these doors should be called the "Beautiful Gate", and in Greek this is the only term used, although the official English sites of the Ecumenical Patriarchate, the Orthodox Church in America and the Antiochian Orthodox Church all use the term "Royal Doors". In Russia, they are sometimes called the "Red Gates", red being synonymous with beautiful.