The Canonization of Saints is the process used by the Roman Catholic Church of recognizing those persons who have lived exemplary lives suitable of identifying them as Christian Saints. The same term also describes the Eastern Orthodox practice of adding the names of saints to the liturgical calendar and to their prayers.
The process of an individual being declared a saint in the Roman Catholic Church began in the 900s, when the church in Rome demanded that saints be added to an official list to be kept in Rome. The first saint to be added to this official list was Saint Ulrich of Augsburg, who was canonized in 993.
The process has evolved and bureaucratized over time into a multi-stage study of the life, writings, and after-life (miracles) of the candidate. The process involves several steps, including beatification and the last is canonization.
In Eastern Orthodoxy, canonization continues to be practiced much as it was during the first millennium of Christianity: People are recognized as saints primarily because they are seen to have preserved the image of God in themselves, and in that sense are living icons. This recognition happens through the simple process of adding a person's name to the list or canon of saints who are honored throughout the year. Canonization does not make a person a saint; canonization simply recognizes that a person is already a saint. There is no single comprehensive list of all Orthodox saints, and no bureaucratic process to go through before adding a saint to the canon.
The process traditionally is a matter of "ripple effect" more than anything. Individual Orthodox Christians may venerate someone on a purely personal level. Eventually, a parish priest or two may include commemoration at the local parish. A Bishop may determine that the saint in question is suitable for commemoration throughout his entire diocese, at which point he will have a "Glorification" ceremony to announce this. A synod of Bishops may determine that the saint is of sufficient importance to be commemorated throughout their jurisdiction or sub-jurisdiction and likewise have a broader Glorification ceremony. Once this has happened, it is usual for most other jurisdictions to simply accept the saint as appropriate for personal veneration, although the saint still might not be added to their calendars. In theory, all synods of all Eastern Orthodox jurisdictions could hold a massive co-Glorification ceremony and announce the suitability of a person to be venerated in all jurisdictions. In practice, addition to additional calendars beyond this point has been a matter of quiet administrative detail.
This usage, canonization, is usually separated from the idea of the formalization of the list of writings accepted by a religious group as inspired or by a cultural group as centrally important for study; the phrase used to describe that process is usually "canon formation" (see Canon, Biblical canon).
It also should not be confused with Wiki Canonization.