Almirantazgo Fjord, Fjord in Magallanes Region, Chile

Almirantazgo Fjord cuts into the west coast of Isla Grande de Tierra del Fuego, running southeast from Whiteside Channel, which separates the island from Dawson Island. On its south side, smaller fjords and bays indent the north coast of the Cordillera Darwin, including Ainsworth Bay, fed by the Marinelli Glacier. The Azopardo River empties into the fjord's head.

The sound was discovered in 1827 by British captain Phillip Parker King, who named it after the British Admiralty. On 28 February 2018, by decree DS No. 11 of the Ministry of the Environment, 76,400 hectares of the sound were declared a Protected Coastal Marine Area under the official protection of the Chilean State.

The fjord's name honours the British Admiralty, given by Phillip Parker King after his 1827 survey. On its north and east shores lie the settlements of Timaukel and Puerto Arturo and several sheep estancias. The south shore borders Alberto de Agostini National Park, and on 28 February 2018 the marine area was declared a protected coastal marine area under decree DS No. 11, covering 76,400 hectares.

The fjord lies on the west coast of Isla Grande de Tierra del Fuego, reached by boat from Puerto Arturo or Timaukel; there are no roads along its shores. Vessels enter from the Whiteside Channel, and Ainsworth Bay, fed by the retreating Marinelli Glacier, is the usual stop for watching elephant seals. The area is remote and weather-exposed, so crossings depend on sea conditions.

The fjord connects Lago Fagnano, shared by Chile and Argentina, with the Strait of Magellan. On 28 February 2018, by decree DS No. 11 of the Ministry of the Environment, 76,400 hectares of the sound were declared a Protected Coastal Marine Area under Chilean state protection.