The royal doors, holy doors, or beautiful gates are the central doors of the iconostasis in an Eastern Orthodox or Eastern Catholic church. 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 or the Archangels Michael and Gabriel. These are the doors that the clergy will normally use when entering the sanctuary. The central double doors are the "holy doors", which are considered to be most sacred, and may only be entered at certain sacred moments during the services, and only by ordained clergy.

In Eastern Orthodox and Byzantine Catholic churches, an entrance is a procession during which the clergy enter into the sanctuary through the Holy Doors. The origin of these entrances goes back to the early church, when the liturgical books and sacred vessels were kept in special storage rooms for safe keeping and the procession was necessary to bring these objects into the church when needed. Over the centuries, these processions have grown more elaborate, and nowadays are accompanied by incense, candles and liturgical fans. In the liturgical theology of the Eastern Orthodox Church, the angels are believed to enter with the clergy into the sanctuary, as evidenced by the prayers which accompany the various entrances.