William Nicholas Keogh (1817–1878) was an Irish politician and judge who played a prominent role in the political and legal landscape of 19th-century Ireland. Born in Galway and educated at Trinity College Dublin, he was called to the Irish Bar in 1840 and achieved the rank of Queen's Counsel in 1849.
Keogh entered politics as the Member of Parliament (MP) for Athlone in 1847. He was a co-founder of the Independent Irish Party, an organization dedicated to advocating for tenant rights and the interests of the Catholic population in Ireland. However, Keogh’s political reputation was significantly impacted in 1852 when he and other members of his party accepted government offices under the Earl of Aberdeen’s coalition ministry. Keogh was appointed Solicitor General for Ireland and later Attorney General for Ireland. This departure from the party's pledge of "independent opposition" was viewed by many Irish nationalists as a betrayal, leading Keogh and his associates to be disparagingly referred to as the "Pope’s Brass Band."
In 1856, Keogh was appointed a Justice of the Court of Common Pleas in Ireland. His judicial tenure was marked by further controversy, most notably his presiding over the 1872 Galway election petition. In his judgment, Keogh delivered a scathing critique of the Catholic clergy's influence on the electoral process, accusing them of "undue influence" and "spiritual intimidation." The judgment provoked intense public hostility and widespread protests across Ireland.
Keogh remained on the bench until shortly before his death. He died in Bingen, Germany, on September 30, 1878. His career remains a subject of study regarding the intersection of religion, law, and nationalist politics in Victorian Ireland.