William Drennan was an Irish physician and writer who moved the formation in Belfast and Dublin of the Society of United Irishmen. He was the author of the Society's original "test" which, in the cause of representative government, committed "Irishmen of every religious persuasion" to a "brotherhood of affection". Drennan had been active in the Irish Volunteer movement and achieved renown with addresses to the public as his "fellow slaves" and to the British Viceroy urging "full and final" Catholic emancipation. After the suppression of the 1798 Rebellion, he sought to advance democratic reform through his continued journalism and through education. With other United Irish veterans, Drennan founded the Belfast [later the Royal Belfast] Academical Institution. As a poet, he is remembered for his eve-of-rebellion When Erin First Rose (1795) with its reference to Ireland as the "Emerald Isle".

The Society of United Irishmen was a sworn association, formed in the wake of the French Revolution, to secure representative government in Ireland. Despairing of constitutional reform, and in defiance both of British Crown forces and of Irish sectarian division, in 1798 the United Irishmen instigated a republican rebellion. Their suppression was a prelude to the abolition of the Irish Parliament in Dublin and to Ireland's incorporation in a United Kingdom with Great Britain.