Base Orcadas is an Argentine scientific station in Antarctica, and the oldest of the stations in Antarctica still in operation. It is located on Laurie Island, one of the South Orkney Islands (Spanish: Islas Orcadas del Sur), at 4 meters (13 ft) above sea level and 170 meters (558 ft) from the coastline. Established by the Scottish National Antarctic Expedition in 1903 and transferred to the Argentine government in 1904, the base has been permanently populated since, being one of six Argentine permanent bases in Argentina's claim to Antarctica, and the first permanently inhabited base in Antarctica.

The nearest Argentine port is Ushuaia, which is 1,502 km (811 nmi) away. The base has 11 buildings and four main topics of research: continental glaciology, seismology, sea-ice-zone glaciology (since 1985) and meteorological observations (since 1903).

Orcadas was the only station on the islands for 40 years until the British established a small summer base, Cape Geddes Station in Laurie Island in 1946, replaced by Signy Research Station in Signy Island in 1947. It also had the first radiotelegraph in the continent in 1927. The 11 buildings of the station house up to 65 people during the summer, and an average of 17 during winter. The scientific activities are carried out at the Laboratorio Antártico Mutidisciplinario en Base Orcadas (LABORC), the "Multidisciplinary Antarctic Laboratory at Base Orcadas".

In 1903 Dr William S. Bruce's Scottish National Antarctic Expedition established Omond House, a meteorological station on Laurie Island. During the expedition, however, the crew became stuck in the ice and, unable to sail off, were trapped in the station for the winter.

Bruce left the station in December of that year for Buenos Aires to fix the ship and obtain supplies, leaving meteorologist Robert C. Mossman in charge of the base to continue the observations.

Bruce offered to the Government of President Julio Argentino Roca the transfer of the station and instruments for the sum of 5.000 pesos, on the condition that the government committed itself to the continuation of the scientific mission. He also offered to transport in his ship the appointed personnel back to the station.

Bruce had informed the British officer William Haggard of his intentions in December 1903. On 29 December, Haggard sent a note to the Argentine Foreign Minister, José Terry, ratifying the terms of Bruce's proposition. Roca submitted the matter to the Oficina Meteorológica Nacional (National Office of Meteorology) who advised him to accept the offer. On January 2, 1904, the installations were accepted through a presidential decree.

The Scotia sailed back for Laurie Island on 14 January 1904 carrying on board Luciano H. Valette, from the Office of Zoology of the Ministry of Agriculture, Edgard C. Szmula, employee of the National Meteorological Office, and Hugo Acuña, from the Ministry of Livestock, who was also designated Postal Chief of the Orkney Islands by the Director General of the National Postal and Telegraphs Office, Manuel García Fernández. Mossman was left in charge of the expedition, along with William Smith as cook.