Nagaoka-kyō(長岡京) was the capital of Japan from 784 to 794. Its location was reported as Otokuni District, Yamashiro Province, and Nagaokakyō, Kyoto, which took its name from the capital. Parts of the capital were in what is now the city of Nagaokakyō, while other parts were in the present-day Mukō and Nishikyō-ku, the latter of which belongs to the city of Kyoto.