The Vistula Spit is an aeolian sand spit, or peninsular stretch of land, separating Vistula Lagoon from Gdańsk Bay, in the Baltic Sea, with its tip separated from the mainland by the Strait of Baltiysk. The border between Poland and Kaliningrad Oblast, an exclave of Russia, bisects it, politically dividing the spit into two pieces between the two countries. The westernmost geographical point of Russia is located on the Vistula Spit. The Polish part contains a number of tourist resorts, incorporated administratively as the town of Krynica Morska.

A spit or sandspit is a deposition bar or beach landform off coasts or lake shores. It develops in places where re-entrance occurs, such as at a cove's headlands, by the process of longshore drift by longshore currents. The drift occurs due to waves meeting the beach at an oblique angle, moving sediment down the beach in a zigzag pattern. This is complemented by longshore currents, which further transport sediment through the water alongside the beach. These currents are caused by the same waves that cause the drift.