Koga

Koga is a Japanese term used as a surname, a place name, and in historical and cultural contexts. As a surname, Koga (variously written with different kanji) is common in Japan and appears among people of Japanese descent worldwide. In geography, Koga most commonly refers to Koga, a city in Ibaraki Prefecture in the Kantō region of Japan.

Historically, the name Kōga (written as 甲賀) is associated with the Kōga region in Ōmi Province, now part of present-day Shiga Prefecture. It is closely linked to the Kōga-ryū (Koga-ryu) school of ninjutsu, one of the best-known ninja traditions in popular culture. The Kōga-ryū is often cited in contrast to the Iga-ryū, another famed ninja lineage, and its legends have enduring influence in folklore, literature, and media.

In modern usage, Koga appears in various contexts beyond a family name and a Japanese city. It is found in fiction and media as character names or place names, and it is used by organizations, businesses, and geographical features that adopt the heritage of the name. The term thus holds multiple, distinct meanings depending on the context, ranging from a specific locality in Japan to a historic ninjutsu tradition and a common surname.