Joseph Campbell (July 15 1879 – June 1944) was an Irish poet and lyricist. He wrote as Seosamh Mac Cathmhaoil (also Seosamh MacCathmhaoil), which has been Anglicised to Joseph McCahill on occasion. He is now remembered best for words he supplied to traditional airs, such as My Lagan Love; his verse was also set to music by Arnold Bax and Ivor Gurney.
He was born in Belfast, into a Catholic and Irish nationalist family from County Down. He was educated at St Malachy's College, Belfast. After working for his father he taught for a while. He travelled to Dublin in 1902, meeting leading nationalist figures. His literary activities began with songs, as a collector in Antrim and working with the composer Herbert Hughes. He was then a founder of the Ulster Literary Theatre in 1904.
He moved to London in 1905, where he was involved in Irish literary activities while working as a teacher. He married in 1910 Nancy Maude, and they moved shortly to Dublin, and then County Wicklow. He took part as a supporter in the Easter Rising of 1916; he became a Sinn Féin Councillor in Wicklow in 1921. Later in the Irish Civil War he was on the Republican side, and was interned in 1922/3. His marriage broke up, and he emigrated to the United States in 1925.