John Lloyd Williams (10 July 1854 – 15 November 1945) was a Welsh botanist, author, and musician.
His research on marine algae, coming to similar conclusions to Camille Sauvageau in France, was not published until 1921, when he was in his sixties.
He also presented a paper to the Honourable Society of Cymmrodorion on 22 January 1908, entitled Welsh National Melodies and Folk-Songs.
In 1906, he had been involved in the creation of the Welsh Folk-Song Society, along with Harry Reichel, Alfred Perceval Graves, and others.
At Bangor he founded a choir of students, "Y Canorion", who specialised in traditional Welsh folk songs.