Robert Plunkett, 5th Baron Dunsany (died 1559) was an Anglo-Irish nobleman of the Tudor period.
He succeeded to the title of Baron of Dunsany in 1521, when his father was killed while assisting the Earl of Surrey, the Lord Lieutenant of Ireland, in putting down a rebellion by the O'Connor and O'Carroll families.
They had at least thirteen children, most of whom survived infancy, including: Dunsany married secondly Jenet Sarsfield, who had already buried two husbands and was to have six in all.
His enemies urged that he should be attainted but in the event Henry VIII, having virtually destroyed the FitzGerald family, including Dunsany's son-in-law Walter, was prepared to be merciful to the other nobles of the Pale, and Dunsany escaped unscathed.
He took his seat in the Irish House of Lords in the Parliament of 1541; he was one of the nobles who confirmed the election of Sir Francis Bryan as Governor of Ireland in 1549; and in 1557 he accompanied the Lord Deputy, Sussex, on an expedition against the McDonnells of Ulster.