| Type: | Bishop |
| Honorific-Prefix: | Most Reverend |
| Sigismondo Isei | |
| Bishop of Comacchio | |
| Church: | Catholic Church |
| Term: | 1655–167 |
| Predecessor: | Giulio Cesare Borea |
| Successor: | Nicolò d'Arcano |
| Ordained By: | 16 September 1645 |
| Consecration: | 12 September 1655 |
| Consecrated By: | Giovanni Battista Maria Pallotta |
| Birth Date: | 1 May 1620 |
| Birth Place: | Cesene, Italy |
| Death Date: | September 1670 |
| Death Place: | Comacchio, Italy |
Sigismondo Isei (1 May 1620 – September 1670) was a Roman Catholic prelate who served as Bishop of Comacchio (1655–1670).[1]
Sigismondo Isei was born in Cesene, Italy on 1 May 1620 and ordained a priest on 16 September 1645.[2] On 30 August 1655, he was appointed during the papacy of Pope Alexander VII as Bishop of Comacchio.On 12 September 1655, he was consecrated bishop by Giovanni Battista Maria Pallotta, Cardinal-Priest of San Pietro in Vincoli, Patrizio Donati, Bishop Emeritus of Minori, Taddeo Altini, Bishop of Civita Castellana e Orte, serving as co-consecrators. He served as Bishop of Comacchio until his death in September 1670.