Nagayama Castle, Ancient castle ruins in Hita, Japan

Nagayama Castle is a hilltop castle (hirayama-jiro) on Mount Tsukikuma, one of Hita's Mikuma Sanzan, in Maruyama-machi, Hita. Its summit honmaru keeps a stone wall of rounded river stones laid in nozura-zumi, with sangi-zumi corners; the ninomaru sat mid-slope and the sannomaru at the foot, with the main gate (otemon) at the south centre. The site is now Tsukikuma Park, and the stone bridge and cut-stone walls on the sannomaru date from the Meiji-era prefectural office and governor's residence.

Ogawa Mitsuuji built the castle around 1601 and named it Maruyama Castle, bringing merchants from Jūnichō village and laying out two north-south streets toward the Nakatsu road. In 1616 Ishikawa Tadafusa, a fudai daimyō, arrived from Ōgaki Castle, rebuilt it as Nagayama Castle and moved the castle town to today's Mameda-machi. It passed to Nakatsu domain in 1633, and in 1639 the Ogawa brothers became first daikan and abolished the castle, building Hita jin'ya below.

The castle hill became Tsukikuma Park in 1915, and the site of the former third bailey later held the Hita Prefectural Office and governor's residence under Matsukata Masayoshi, who became Japan's fourth prime minister. The name Tsukikuma Castle appears in volume eight of the Bungo Kokushi. The castle was also called Mameda Castle.

The castle site is on Mount Tsukikuma, one of the Mikuma Sanzan hills north of central Hita. The summit honmaru is reached on foot via a climbing path; part of the trail collapsed in the July 2012 Kyushu floods. The former jinya grounds along the Otemon moat are now a residential area with no remains.

The honmaru's surviving stone walls use river stones in nozura-zumi style, with sangi-zumi corners; a 2009 survey dated the main gate wall to the 1680s. Excavations in 2011 and 2012 uncovered foundation stones and a section of the Higo-dono moat wall. The 2016 Kumamoto earthquake toppled two sections of the honmaru wall, the largest cultural-property damage in Oita Prefecture.