“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.
There are now several versions in the O’Connor Music Store if you are interested in learning this Christmas carol.