Adeste Fideles

O Come, All Ye Faithful
A congregation in England sings the song during Christmas 2006
Native name	Adeste Fideles
Genre	Christmas
Language	Latin

"O Come, All Ye Faithful" (originally written in Latin as Adeste Fideles) is a Christmas carol which has been attributed to various authors, including John Francis Wade (1711–1786), John Reading (1645–1692) and King John IV of Portugal (1604–1656), with the earliest manuscript of the hymn bearing his name, located in the library of the Ducal Palace of Vila Viçosa.

The original four verses of the hymn were extended to a total of eight, and these have been translated into many languages. The English translation of "O Come, All Ye Faithful" by the English Catholic priest Frederick Oakeley, written in 1841, is widespread in most English speaking countries. The present harmonisation is from the English Hymnal (1906).

An original manuscript of the oldest known version, dating from 1751, is held by Stonyhurst College in Lancashire.

Besides John Francis Wade, the tune has been purported to be written by several musicians, from John Reading and his son to Handel and even Gluck, including the Portuguese composers Marcos Portugal or the king John IV of Portugal himself. Thomas Arne, whom Wade knew, is another possible composer. There are several similar musical themes written around that time, though it can be hard to determine whether these were written in imitation of the hymn, the hymn was based on them, or they are totally unconnected.

Wade included it in his own publication of Cantus Diversi (1751). It was published again in the 1760 edition of Evening Offices of the Church. It also appeared in Samuel Webbe's An Essay on the Church Plain Chant (1782).