Zaika-ji, Buddhist temple in Toyokawa, Japan.

Zaika-ji is a Koyasan Shingon temple on the slopes of Kannon-yama in the Zaika district of Toyokawa, Aichi Prefecture. Its buildings stand in three groups linked by approach paths: the main hall on the upper terrace, the Monju hall on the middle terrace, and the Niomon gate with the head priest's quarters below. The main hall, rebuilt in 1823 by carpenter Okada Gozaemon, is a wooden single-storey building with a copper-sheet roof.

According to the temple's 1799 origin narrative, Gyōki founded it in 724 by imperial order of Emperor Shōmu, carving the main Senju Kannon; Kūkai restored it as a Shingon temple in the Kōnin era. The extant Kongō Rikishi statues date to the late 11th or early 12th century. In 1472 Makino Koshaku moved the main hall from Imamiya to its present site, and Tokugawa Ieyasu later granted the temple over 160 koku and 36 chō of mountain forest.

The temple's name is written with the characters for 'wealth' and 'congratulation'. Its guardian shrine, Hachisho Jinja, stands behind the main hall and enshrines eight deities, including Hiyoshi, Hachiman and Atsuta; its 1724 main hall and 1826 worship hall show the mixture of Shinto and Buddhism. The Goma rite for Monju is held on the 25th of each month.

The halls are split across three areas on the slope of Mount Kannon: the main hall on the upper terrace, the Monju hall at mid-level and the Niō gate and main quarters below, linked by approach paths. The grounds are wooded and uneven, so allow time for walking between them. The temple is in Zaika-chō, Toyokawa, and is reached by road rather than by train.

The Nio gate was long planned as a two-storey tower, but the upper storey was never built, as its eaves show. The gate was dismantled and repaired from 1996 to 1998, and when work finished in October 1998 a ring-entering ceremony was offered by yokozuna Takanohana. The temple's two Nio statues, 381 cm and 375 cm tall, are among the largest in Japan after those of Todai-ji and Tané-ji.