The Fourth Kuril Strait (Russian: Четвёртый курильский пролив) is a very deep strait separating the islands of Onekotan and Paramushir in the Kuril Islands, Russia. It is 46.7 km (about 29 mi) wide. It was formerly known as the Amphitrite Strait.[1] The flood tidal current in the strait sets west-northwest, while the ebb flows in the opposite direction. These currents may reach over two knots.[2]