| Jurisdiction: | Diocese |
| Iaşi | |
| Latin: | Dioecesis Iasensis |
| Local: | Episcopia de Iaşi |
| Country: | Romania |
| Province: | Bucharest |
| Area Km2: | 46,378 |
| Population: | 4,272,000 |
| Population As Of: | 2013 |
| Catholics: | 234,211 |
| Catholics Percent: | 5.5 |
| Denomination: | Catholic Church |
| Established: | 27 June 1884 |
| Cathedral: | Our Lady Queen of Iași Cathedral, Iaşi |
| Bishop: | Iosif Păuleț |
| Bishop Title: | Bishop |
| Metro Archbishop: | Ioan Robu |
| Suffragan: | for one --> |
| Auxiliary Bishops: | Petru Sescu |
| Vicar General: | Petru Sescu |
| Archdeacon: | for one--> |
| Map: | Romanian Roman-Catholic Church map.svg |
| Map Size: | 250px |
| Website: | Website of the Diocese |
The Diocese of Iași (or Latin: Dioecesis Iassiensis, Romanian; Moldavian; Moldovan: Episcopia Romano-Catolică de Iași, Hungarian: Jászvásári Egyházmegye, Polish: Diecezja Jassy) is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Romanian Western Moldavia. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Bucharest. Its episcopal see is Iași.
Its bishop has been Iosif Păuleț since 2019. Between 1990 and 2019 its bishop was Petru Gherghel, previously Apostolic Administrator since 1978. Auxiliary Bishop since 1999 has been Aurel Percă, Titular Bishop of Mauriana, appointed Archbishop of Bucharest in 2019.
It was established in 1818 as the Apostolic Vicariate of Moldavia (a pre-diocesan missionary jurisdiction; exempt, i.e. directly subject to the Holy See, not part of an ecclesiastical province, but entitled to a titular bishop), on territory split off from the suppressed Diocese of Bacău, which had originally been set up at Siret by Pope Urban V in 1370, due to work done by Franciscans and Dominicans; its seat was transferred to Bacău at the beginning of the 15th century. Abandoned in 1497 due to Muslim persecutions, the See of Bacău was re-established in 1611, and had a succession of twenty prelates until 1789, when it was suppressed. The Catholics of Moldavia were then placed under the spiritual direction of Apostolic prefects, generally chosen from the Conventuals in charge of the mission.
The Apostolic Vicariate of Moldavia was promoted on 27 June 1884 by Pope Leo XIII to Diocese of Iaşi (Jászvásár in Hungarian) covering Romanian Moldavia, with Iaşi as residence.
In 1921 it gained territory from the Diocese of Tiraspol.On 5 June 1930 it gained territory from the Ukrainian Latin Metropolitan Archdiocese of Lviv.
On 28 October 1993, it lost territory to establish the Apostolic Administration of Moldova (now the diocese of Chișinău).
Its cathedral is the Our Lady Queen of Iași Cathedral, in Iaşi. The former cathedral, Assumption of Mary Church, is also located in the city.
Other former cathedrals are the Biserica de vizitarea Maicii Domnului, in Bacău, and the ruined Biserica de Maicii Domnului, in Baia.
A minor basilica is the Bazilica Minora Sanctuarul de la Cacica, in Cacica.
, its pastorally served 232,132 Catholics (5.3% of 4,359,762 total) on 46,378 km2 in 149 parishes, 420 priests (297 diocesan, 123 religious) with 704 lay religious (282 brothers, 422 sisters) and 125 seminarians.
The diocese covers the Romanian region of Moldavia - the counties of Suceava, Botoșani, Neamț, Iași, Bacău, Vaslui, Vrancea and Galați.
5.2% of the inhabitants are Catholic, with concentrations around Bacău and Roman. Its adherents are predominantly ethnic Romanians, with small Csángós (old Hungarian dialect) and Polish communities.