Koyu District, Miyazaki

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File:Koyu District in Miyazaki Prefecture.png

{{nihongo|Koyu|児湯郡|Koyu-gun}} is a district in Miyazaki Prefecture, Japan.

As of October 1, 2019, the district has an estimated population of 68,269 and the density of 95.5 persons per km². The total area is 715.03 km².