Yodogawa Ōzeki, Weir on the Yodo River in Miyakojima-ku, Osaka, Japan

Yodogawa Ōzeki is a movable weir on the main stream of the Yodo River, the lowest river facility on the river, spanning the boundary of Miyakojima-ku and Higashiyodogawa-ku in Osaka. Completed in 1983, it replaced the Naga movable weir of 1964 and is managed jointly by the Kinki Regional Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism and the Water Resources Agency. Its gates supply tap water and industrial water to Osaka, Hyogo and the Hanshin industrial belt.

The structure was built in 1983 in response to water quality challenges in Osaka during rapid urban growth. Its construction was part of broader efforts to improve the city's infrastructure for a growing population.

The weir's releases feed the old Yodo River and its branches, the Kizu, Aji and Dōtonbori, and supply the moat of Osaka Castle. Its operators vary the flow through the day, sending about 100 tonnes per second at high tide and 40 at low tide, averaging 60, to flush stagnant water toward Osaka Bay. This artificial flood release is called flash discharge.

The weir stands just upstream of the old Yodo River branch point, between Kema 4-chome in Miyakojima-ku and Kunijima 2-chome in Higashiyodogawa-ku. The nearest station is Kunijima on the Hankyu Senri Line; by car, exit at the Nagahe interchange of the Hanshin Expressway Route 12 Moriguchi Line. The surrounding riverbed is maintained as open ground and is used by local residents for walks.

The weir releases water at 100 tonnes per second at high tide in Osaka Bay and 40 tonnes per second at low tide, averaging 60 tonnes per second. This deliberate surge, called flush discharge, pushes stagnant water from the old Yodo River and its channels into the bay.