O For A Thousand Tongues To Sing is a Christian hymn written by Charles Wesley. Charles Wesley wrote over 6,000 hymns, many of which were subsequently reprinted, frequently with alterations, in hymnals, particularly those of the Methodist Church.

Charles Wesley was suffering a bout of pleurisy in May, 1738, while he and his brother were studying under the Moravian scholar Peter Bohlart in London. At the time, Charles was plagued by extreme doubts about his faith. Taken to bed with the sickness on May 21st, Charles was attended by a group of Christians who offered him testimony and basic care, and he was deeply affected by this. He read from his Bible and found himself deeply affected by the words, and at peace with God. Shortly his strength began to return. He wrote of this experience in his journal and counted it as a renewal of his faith; when his brother John had a similar experience on the 24th, the two men met and sang a hymn Charles had written in praise of his renewal.

One year from the experience, Charles was taken with the urge to write another hymn, this one in commemoration of his renewal of faith. This hymn took the form of a 19-stanza poem, called O For A Thousand Tongues To Sing, and was published with the recommendation for singing "on the anniversary of one's conversion."

The hymn first appeared in print in Charles' Hymns and Sacred Poems published in 1740, and was placed first in John Wesley's A Collection of Hymns for the People Called Methodists published in 1780. It has appeared first in every Methodist hymnal since that time.

Originally published with all 19 verses, the hymn today is traditionally condensed into 6 stanzas, beginning with the seventh stanza of Wesley's poem. It is most commonly sung to Lowell Mason’s 1839 arrangement of the tune Azmon , written by Carl G. Glaser in 1828. Mason's arrangement was written as a setting for this hymn. Most hymnals that include the hymn also include the entire text of the original poem on a separate page.