The Scotia plate (Spanish: Placa Scotia) is a minor tectonic plate on the edge of the South Atlantic and Southern oceans. Thought to have formed during the late Eocene with the opening of the Drake Passage that separates Antarctica and South America, it is a minor plate whose movement is largely controlled by the two major plates that surround it: the Antarctic plate and the South American plate. The Scotia plate takes its name from the steam yacht Scotia of the Scottish National Antarctic Expedition (1902–04), the expedition that made the first bathymetric study of the region.

Roughly rhomboid, extending between 50°S 70°W / 50°S 70°W / -50; -70 and 63°S 20°W / 63°S 20°W / -63; -20, the plate is 800 km (500 mi) wide and 3,000 km (1,900 mi) long. It is moving WSW at 2.2 cm (0.87 in)/year and the South Sandwich plate is moving east at 5.5 cm (2.2 in)/year in an absolute reference frame. Its boundaries are defined by the East Scotia Ridge, the North Scotia Ridge, the South Scotia Ridge, and the Shackleton fracture zone.

The Scotia plate is made of oceanic crust and continental fragments now distributed around the Scotia Sea. Before the formation of the plate began 40 million years ago (40Ma), these fragments were at least partly exposed above the water, and formed a continuous landmass from Patagonia to the Antarctic Peninsula along an active subduction margin. It served as one end of the Antarctic land bridge, a wider land bridge that connected South America, Antarctica, and Australia. At present, the plate is almost completely submerged, with only the small exceptions of South Georgia on its northeastern edge and the southern tip of South America.

Together with the South Sandwich plate, the Scotia plate joins the southernmost Andes to the Antarctic Peninsula, just like the Caribbean plate joins the northernmost Andes to North America, and these two plates are comparable in several ways. Both have volcanic arcs at their eastern ends, the South Sandwich Islands on the Sandwich Plate and the Lesser Antilles on the Caribbean plate, and both plates also had a major impact on global climate when they closed the two major gateways between the Pacific and Atlantic Oceans during the Mesozoic and Cenozoic.

The northern edge of the Scotia plate is bounded by the South American plate, forming the North Scotia Ridge. The North Scotia ridge is a left-lateral, or sinistral, transform boundary with a transform rate of roughly 7.1 mm/yr. The Magallanes–Fagnano Fault is passing through Tierra del Fuego.

The northern ridge stretches from Isla de los Estados off Tierra del Fuego in the west to the microcontinent South Georgia in the east, with a series of shallow banks in between: Burdwood, Davis, Barker, and Shag Rocks. North of the ridge is the 3 km (1.9 mi) deep Falkland Trough.

Experts in plate tectonics have been unable to determine whether the South Georgian Islands are part of the Scotia plate or have been recently accreted to the South American plate. Surface expressions of the plate boundary are found north of the islands suggesting a long-term presence of the transform fault there. Yet seismic studies have identified strain and thrusting south of the islands indicating the possible shift of the transform fault to an area south of the island. It has also been suggested that the plate bearing the islands may have broken off from the Scotia plate, forming a new independent South Georgia microplate, yet there is little evidence to make this conclusion.

The South Georgia microcontinent was originally connected to the Roca Verdes back-arc basin (southernmost Tierra del Fuego) until the Eocene. Before that, this basin went through a series of geological transformations during the Cretaceous, through which South Georgia was first buried, then made a topographic feature again by the Late Cretaceous. At about 45 Ma, South Georgia, still part of the South American plate, got buried again and something, possibly rotation of the Fuegian Andes, completed the break-up and allowed South Georgia a second exhumation. During the Oligocene (34–23 Ma) South Georgia was reburied again as seafloor spreading took place in the West Scotia Sea. 10 Ma, finally, the South Georgia microcontinent was uplifted as a result of the collision with the Northeast Georgia Rise.