The Roman Catholic Diocese of Kyiv-Zhytomyr (Latin: Dioecesis Kioviensis-Zytomeriensis) is a suffragan diocese of the Latin Church of the Catholic Church in Ukraine in ecclesiastical province of the Metropolitan Archdiocese of Lviv of the Latins.

Its cathedral episcopal see is the St. Sophia's Cathedral, Zhytomyr.

It also has, both in Kyiv: a Co-Cathedral of St. Alexander, and a former cathedral, now Church of St. Nicholas.

--- As per 2014, it pastorally served 219,600 Catholics (2.7% of 8,182,668 total) on 111,600 km² in 162 parishes and 124 missions with 160 priests (60 diocesan, 100 religious), 277 lay religious (112 brothers, 165 sisters) and 36 seminarians.

(all Roman Rite) / exempt Armenian Catholic Ordinariate of Eastern Europe, directly dependent on the Holy See / Ruthenian Catholic Eparchy of Mukacheve