| Jurisdiction: | Diocese |
| Yokohama | |
| Local: | Japanese: カトリック横浜教区 |
| Latin: | Dioecesis Yokohamaensis |
| Country: | Japan |
| Territory: | Kanagawa, Shizuoka, Nagano, and Yamanashi |
| Metropolitan: | Tokyo |
| Province: | Tokyo |
| Cathedral: | Cathedral of the Sacred Heart in Yokohama |
| Established: | 9 November 1937 |
| Area Km2: | 28,246 |
| Population: | 15,763,428 |
| Population As Of: | 2015 |
| Catholics: | 55,723 |
| Catholics Percent: | 0.4 |
| Parishes: | 93 |
| Priests: | 46 diocesan (and 54 religious) |
| Sui Iuris Church: | Latin Church |
| Rite: | Roman Rite |
| Bishop: | Rafael Masahiro Umemura |
| Metro Archbishop: | Tarcisio Isao Kikuchi |
| Map: | Giappone - Diocesi di Yokohama.png |
| Website: | yokohama.catholic.jp |
The Diocese of Yokohama (Latin: Dioecesis Yokohamaensis, Japanese: カトリック横浜教区) is a Latin Church diocese of the Catholic Church. Its cathedral is located in the city of Yokohama. It is a suffragan diocese of Roman Catholic Archdiocese of Tokyo in Japan and therefore in Tokyo's ecclesiastical province.
There have been two dioceses in Yokohama. On January 5, 1846, the Apostolic Vicariate of Japan was established.[1] This became the Apostolic Vicariate of Northern Japan in 1876 and then was suppressed in 1891 to establish the Archdiocese of Tokyo.
On November 11, 1937, the Diocese of Yokohama was erected out of territory of the Archdiocese of Tokyo. The new diocese covered eight prefectures of Japan: Kanagawa, Ibaraki, Tochigi, Gumma, Saitama, Yamanashi, Nagano and Shizuoka. On January 4, 1939, four of those prefectures – Saitama, Ibaraki, Tochigi and Gumma – were moved to the newly formed Apostolic Prefecture of Urawa, now the Roman Catholic Diocese of Saitama.
The Bishops of the diocese have been: