Kōka (甲賀郡) was a district located in Shiga Prefecture, Japan. As of 2003, the district had an estimated population of 147,928 and a density of 267.90 persons per km2. The total area was 552.18 km2. From circa 1460 until 1574, during the Sengoku period, the district was effectively independent of centralized state control and operated as the Kōka-gun Chūsō, a military confederacy of jizamurai and other warrior families that became known as ninja. During this period it formed an alliance with its southern neighbor, the Iga Sokoku Ikki, a similar independent confederacy of ninja families. Both alliance and the ikki ended when Oda Nobunaga defeated Kōka and compelled it to be a vassal.

Towns and villages

Before the dissolution in 2004, the district had seven towns as listed below. Each municipality is now a part of the city noted in the parentheses.

Mergers