The existence and evolution of a Messinian salt giant in the Mediterranean Sea has caused much debate in the marine science community. Especially the suggestion that the Mediterranean was a deep desiccated basin during the Messinian Salinity Crisis (MSC, 5.97–5.33 Ma), triggered by a temporal disconnection from the global ocean, made it a well-known crisis beyond the scientific boundaries. Approximately ~50 years after this provocative statement, it remained unknown which Mediterranean–Atlantic seaway delivered the 5–6% of the global ocean's salt into the Mediterranean basin. Here, we review the changes in Mediterranean-Atlantic connectivity throughout the late Miocene in order to locate, date and quantify the missing Messinian gateway that provided the salt water inflow during the MSC. We conclude that all the known pre-MSC gateways through southern Spain and northern Morocco were closed, leaving the “Gibraltar Corridor” at its Messinian configuration as the sole candidate. We consider the possibility of longer and narrower straits existing at depth below the present Gibraltar region, and using strait dynamic theory we calculate its dimensions during the Messinian based on the salinity changes in the Mediterranean. A marine Messinian gateway through the Gibraltar Corridor is in agreement with growing evidence that Atlantic waters reached the Mediterranean Sea during all three stages of the MSC.