| Type: | Bishop |
| Honorific-Prefix: | Most Reverend |
| Ascanio Castagna | |
| Bishop of Isola | |
| Church: | Catholic Church |
| Diocese: | Diocese of Isola |
| Predecessor: | Giovanni Antonio Massimo |
| Successor: | Alessandro Bichi |
| Consecration: | 11 September 1622 |
| Consecrated By: | Ottavio Bandini |
| Birth Date: | 1567 |
| Birth Place: | Turin, Duchy of Savoy |
| Death Date: | 16 December 1627 (age 60) |
| Death Place: | Isola, [Kingdom of Naples]] |
| Nationality: | Italian |
Ascanio Castagna (1567 – 16 December 1627) was a Roman Catholic prelate who served as Bishop of Isola (1622–1627).[1]
Ascanio Castagna was born in Turin, Italy in 1567.[2] On 8 August 1622, he was appointed during the papacy of Pope Gregory XV as Bishop of Isola. On 11 September 1622, he was consecrated bishop by Ottavio Bandini, Cardinal-Bishop of Palestrina, with Ulpiano Volpi, Bishop of Novara, and Alessandro Guidiccioni (iuniore), Bishop of Lucca, serving as co-consecrators. He served as Bishop of Isola until his death on 16 December 1627.