Ugashik Bay is a bay of the Bering Sea in the U.S. state of Alaska. It is an elongated, comma-shaped estuary formed where the Ugashik River empties into Bristol Bay, on the western coast of the Alaska Peninsula. Its waters are characteristically turbid and turbulent, the result of muddy feeder streams, frequent winds, and very high tides. Some Bristol Bay tides are thought to rank eighth highest in the world, and Ugashik Bay is greatly influenced by this tidal action.