David John Thomas (1881 - 1928), often known by his bardic name of "Afan", was a Welsh composer, conductor and organist.

Thomas is remembered mainly for his hymn-tunes and songs such as "Drosom ni" and "Cymru fach i mi". Other works include a cantata, "Merch y llyn" ("Lady of the Lake"), and a choral work, "He fell among thieves", with words by Sir Henry Newbolt.