Ottavio Mirto Frangipani (11 April 1544 – 24 July 1612) was an Italian bishop and papal diplomat, who as papal nuncio to Cologne (1587–1596) and to Brussels (1596–1606) oversaw the implementation of Tridentine reforms in the Rhineland and the Spanish Netherlands after the disruptions of the sixteenth century.
Frangipani was born in Naples on 11 April 1544 to Silvio Mirto and Laura della Gatta.
As a result of his experience in Cologne he pressed for the creation of a nunciature in Brussels, arriving there as nuncio on 11 February 1596.
He was active in promoting the restoration of Catholic life in the war-torn Southern Netherlands, visiting Antwerp, Arras, Liège, Namur, Tournai, Cambrai, Calais, Lille, Dunkirk and Gravelines.
His correspondence as nuncio to Brussels has been published as three volumes in the series Analecta Vaticano-Belgica, Nonciature de Flandre, the first edited by Leon van der Essen (1924) and the other two by Armand Louant (1932, 1942).