Château de Gakudenjo, Japanese castle site in Inuyama, Aichi, Japan

Gakudenjo Castle was a flatland castle in what is now Gakuden, Inuyama, Aichi Prefecture, not near Komaki. Almost no remains survive: the site became the grounds of Gakuden Elementary School, and the castle keep platform (tenshudai) was removed in 1980 for a school playground. Only a relocated stone monument and an earthen rampart remain.

Gakudenjo was built in the Eisho era by Oda Hisanaga, deputy shugo of Owari, and became the seat of the Oda of Gakuden. In the early Eiroku era Oda Nobuhide's kinsman Oda Nobukiyo took it and made it an outpost of Inuyama Castle; after Nobukiyo broke with Nobunaga in 1562, Sakai Masahisa held it, then Kajikawa Takamori. It served as a front-line base in the Komaki-Nagakute campaign, where Hashiba Hideyoshi's general Hori Hidemasa and Hideyoshi himself camped, and was abandoned after the war.

The name Gakuden comes from the district of Niwa County in Owari Province where the castle stood, today the Gakuden area of Inuyama, Aichi Prefecture. According to the Oina Monogatari, in 1558 a roughly five-metre earthen platform was raised inside the castle and topped with a two-storey tower called a denshu, where Buddhist and Shinto deities were enshrined.

The site lies in the Gakuden district of Inuyama, Aichi, about five minutes on foot south of Gakuden Station on the Meitetsu Komaki Line. Almost nothing of the castle survives: the honmaru area became the grounds of Gakuden Elementary School, and in 1980 the stone base of the keep was removed to make room for the school playground. Only a relocated stone monument and a remnant earthen rampart remain.

Gakudenjo is the earliest castle in written records said to have had a building called a tenshu: in 1558 a roughly 5-metre earthen platform was raised inside the castle and topped with a two-storey yagura housing Shinto and Buddhist images, called a denshu. The site now lies under Gakuden Elementary School; a relocated monument and an earthen rampart are all that remain.