Mizuwakasu Shrine, Shinto shrine in Okinoshima, Japan.

Mizuwakasu Shrine is a Shinto shrine in the Kori area of Okinoshima, Shimane Prefecture. Its main hall, built in 1795, is a thatched Oki-zukuri structure with a gabled, side-entrance body, crossed finials and a pent roof over the front. In front stands a hall with a green-grey metal roof, lattice panels and a veranda, hung with twisted straw ropes and white paper streamers.

The shrine's founding documents were lost in medieval wars, but a 1688 chronicle records a tradition that the deity landed at Igo and was moved by white doves. In 842 it was listed among official shrines, and by 927 the Engishiki named it a Myojin Taisha. A 1676 flood destroyed the buildings, and they were rebuilt at the present site in 1678.

The shrine's name is written 水若酢, though a Meiji-era survey noted the original form was 水若咋, with 酢 a later substitution. Its biennial Goka Festival, held in even years, features the yamabiki shinji, in which children under eight pull a float called Hōraizan to the otabisho, alongside mikomai, shishimai and yabusame. The festival is one of Oki's three great matsuri and a Shimane Prefecture intangible folk cultural property.

The shrine stands at 723 Kori, Okinoshima, about 20 km north of Saigo Port. Buses from the port stop at Mizuwakasu-jinja-mae after roughly 40 minutes, but departures are few, so check return times before setting out. The precinct also holds the Mizuwakasu Shrine kofun cluster, including a 20 m round tomb behind the main hall.

The shrine grounds hold two burial mounds. Mound No. 1, east of the hall, contains a corridor-style stone chamber about 11 metres long, the largest in the Oki Islands, found in 1920 when a pond was filled in; the pond was the mound's surrounding moat. Swords, iron arrowheads and glass beads came from it.