Final answer:
The Beagle Channel is the strait separating Isla Grande De Tierra del Fuego from the southern islands in the Tierra del Fuego archipelago.
Step-by-step explanation:
The strait that separates the main island of Isla Grande De Tierra del Fuego from the smaller islands archipelago to the south is the Beagle Channel. This strait is a navigable passage in the southern Tierra del Fuego archipelago on the extreme southern tip of South America, mostly between Chile and Argentina.
The Beagle Channel, even though it might not be as widely recognized as the Strait of Gibraltar, is significant in its own right as it delineates part of the border between the two countries and is a critical navigational route for ships that are too large to use the Panama Canal or are avoiding the treacherous Drake Passage.