Nagai Ayame Park, Botanical garden in Nagai, Japan.

Nagai Ayame Park is a city park in Nagai, Yamagata Prefecture, with about 500 varieties and one million Japanese iris plants. Despite the name, the flowers are Japanese iris (hanashōbu), not true ayame. The park also holds the locally discovered Nagai koshu varieties, 34 of which are registered and 13 designated city natural monuments.

In 1910 Kaneda Katsumi planted a few dozen wild irises on a former cedar grove in Yokomachi and invited guests to a tea gathering. In 1912 cedars were felled and more irises set out, forming the park's core. In 1962 visiting iris specialists found varieties matching neither Edo, Higo nor Ise types and named them Nagai koshu.

The park's name says ayame (iris), but the flowers in bloom are strictly hanashōbu, Japanese water iris. During the annual iris festival, held while the flowers peak from mid-June to early July, a local products hall, volunteer guides and the Ayame Kaikan rest house open on the grounds.

The park is a three-minute walk from Ayame-Kōen Station on the Yamagata Railway Flower Nagai Line, and about 60 minutes by car from Yamagata Zao IC via Route 348. Outside the iris festival it stays open all day; during the festival hours are 9:00 to 18:00. In winter snow makes entry impossible.

The park preserves rare local iris varieties that have been cultivated in the region for generations and exist nowhere else in this form. These special breeds represent a living record of the area's gardening heritage.