'O Come, All Ye Faithful' (originally written in Latin as 'Adeste Fideles') is a Christmas carol that has been attributed to various authors, including John Francis Wade (1711–1786), John Reading (1645–1692), King John IV of Portugal (1604–1656), and anonymous monks.

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 original text of the hymn has been from time to time attributed to various groups and individuals, including St. Bonaventure in the 13th century or King John IV of Portugal in the 17th.

It was more commonly believed that the text was written by Cistercian monks, the German, Portuguese or Spanish provinces of that order having at various times been credited.

In modern English hymnals, the text is usually credited to John Francis Wade, whose name appears on the earliest printed versions. However, this is most likely an error of attribution.

In 1751 he published a printed compilation of his manuscript copies, 'Cantus Diversi pro Dominicis et Festis per annum'. This is the first printed source for 'Adeste Fideles'.

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