James MacGeoghegan (1702 at Uisneach, Westmeath, Ireland – 1763 at Paris) was an Irish Roman Catholic priest and historian.
He came of the Geoghegan family long settled in Westmeath and long holding a high position among the Leinster chiefs, and was related to Richard MacGeoghegan, who defended the Castle of Dunboy against Carew, and also to Connell MacGeoghegan, who translated the Annals of Clonmacnoise, as well as to Francis O'Molloy, author of the Lucerna Fidelium.
MacGeoghegan went abroad, and received a Catholic education at the Lombard College (later the Irish College, Paris), and in due course was ordained priest. Then for five years he filled the position of vicar in the parish of Possy, in the Diocese of Chartres, "attending in choir, hearing confessions and administering sacraments in a laudable and edifying manner".
In 1734, he was elected one of the provisors of the Lombard College, and subsequently was attached to the church of St-Merri in Paris. He was also for some time chaplain to the Irish troops in the service of France.
He wrote a History of Ireland. It was written in French and published at Parish in 1758. It was dedicated by the author to the Irish Brigade, and claims that during the fifty years following the Treaty of Limerick (1691) no fewer than 450,000 Irish soldiers died in the service of France. MacGeoghegan was shut out from access to the manuscript materials of history in Ireland, and had to rely chiefly on Lynch and John Colgan. John Mitchel's 1869 History of Ireland professes to be merely a continuation of MacGeoghegan, though Mitchel is throughout much more of a partisan than MacGeoghegan.