What channel forms part of the border between Argentina and Chile in Tierra del Fuego?

The Beagle Channel forms part of the border between Argentina and Chile in Tierra del Fuego.

This east–west strait runs through the Tierra del Fuego Archipelago, separating the main island, Isla Grande de Tierra del Fuego, from islands farther south such as Navarino, Picton and Nueva. Its eastern section is shared by Argentina and Chile, while much of the western section lies entirely within Chile.

The channel takes its name from HMS Beagle, the British surveying vessel associated with voyages in the region. Robert FitzRoy commanded the Beagle during its later survey expedition, when Charles Darwin was aboard as a naturalist. The channel is about 240 kilometres long and connects waters of the Pacific and Atlantic systems.

A frequent mistake is choosing the Strait of Magellan. That passage lies north of Tierra del Fuego and is also associated with Chile, but it is not the channel that forms the Argentina–Chile boundary in this question. The 1984 Treaty of Peace and Friendship helped settle the modern maritime boundary.