Candlemas Island is a small uninhabited island of the Candlemas Islands in the South Sandwich Islands. It is one of about a dozen islands that make up the South Sandwich island arc, a chain of volcanoes in the Southern Ocean that was discovered in 1775 by James Cook. The volcanism is caused by the subduction of the South American Plate beneath the Sandwich Plate. The island is remote and rarely visited due to the often hostile weather conditions, but is populated by penguins and seabirds, which form large breeding colonies.

The island consists of two parts. The southeastern part is older and consists of the heavily glaciated volcanoes Mount Andromeda - with 550 metres (1,800 ft) elevation the highest point of the island - and Mount Perseus, and shows no evidence of recent activity. The northwestern part features the younger scoria cone complex Lucifer Hill, which is surrounded by lava flows. Some of the lava flows may have been emplaced during the 20th century. The older rocks consist mostly of basalt and basaltic andesite, while the younger rocks are predominantly andesite and dacite; the two groups share a common magma formation process.

The Lucifer Hill complex features numerous fumaroles which emit volcanic gases. A vegetation community consisting of mosses and lichens grows around the fumaroles, with some members extending to non-fumarolic terrain.

Candlemas Island is one of the South Sandwich Islands, a 320 kilometres (200 mi) long north–south trending island arc to the southeast of South Georgia and the Falklands. They include Zavodovski, Leskov Island, Visokoi, Candlemas and Vindication Island, Saunders Island, Montagu Island, Bristol Island and Freezland Rock, Bellingshausen Island, Cook Island and Thule Island. All the islands are small and volcanic, most showing evidence of activity during the last two centuries. They are subject to intense marine erosion. Submarine volcanoes include Protector Shoals at the northern end and Nelson and Kemp seamounts at the southern end of the island chain.

The island is also known as Lichtmess-Insel and Candelaria. It is rarely visited owing to the hostile weather and sea conditions, and the south and southeast coasts are hardly accessible; tourist vessels occasionally land on Candlemas. Longline fishing takes place in the surrounding waters. Politically, South Georgia and the South Sandwich Islands make up the UK Overseas Territory of South Georgia and the South Sandwich Islands. In 2012, a marine protected area was established in the South Sandwich Islands. The scope of the protected area was further expanded in 2019.

With dimensions of 6 by 4 kilometres (3.7 mi × 2.5 mi), Candlemas is the third-largest of the South Sandwich Islands and consists of a southeastern, roughly square-shaped half and an irregularly shaped northwestern half. Vindication Island to the west is separated from Candlemas by the shallow (24 metres (79 ft)-27 metres (89 ft)) 3.7 kilometres (2.3 mi) wide Nelson Channel. Visokoi lies 42 kilometres (26 mi) north and Saunders 76 kilometres (47 mi) south of Candlemas Island.

The northwestern half consists of a complex of scoria cones named Lucifer Hill (also known as Lucifer Hills), which reach a maximum elevation of 232 metres (761 ft), 229 metres (751 ft) or 140 metres (460 ft) above sea level. Two main craters with depths of about 15 metres (49 ft) and diameters of 137 metres (449 ft) flank the main summit, which has a flat top. A subsidiary crater lies on the southwestern flank. They are surrounded by five lava flows, the eastern of which is old and covered with volcanic ash while the northern one is younger, with an irregular surface featuring blocks, ridges and gullies. The lava flows are morphologically aa lavas. The eastern lava flow forms Breakbones Plateau, while a northwestward extending lava flow constitutes the Vulcan Point peninsula. The southwestward and northwestward extending lava flows enclose the Tow Bay; Cauldron Pool lies just east of Tow Bay. Another unnamed pool lies at the end of Clinker Gulch on Lucifer Hill, and there are freshwater pools throughout the island. The coastline is formed by cliffs with interspersed recesses and bays.

The southeastern half is the larger and consists of an extinct and eroded stratovolcano. A north-south trending ridge has two summits, the northeastern 455 metres (1,493 ft) high Mount Perseus and the southeastern Mount Andromeda; the latter is the highest point of Candlemas with 550 metres (1,800 ft) or 557 metres (1,827 ft) elevation. This half is asymmetric, rising from west to east, which may indicate that it is the remnant of a formerly larger volcano that was centered east of the current island. Glaciers cover most of the southeastern half of Candlemas, an area of 4.2 square kilometres (1.6 sq mi) as of 1964^[update] which amounts to 40% of the island. The ice reaches thicknesses of 23 metres (75 ft) in coastal cliff exposures. On the southern and eastern side of Candlemas, the ice descends to the sea, in the north it forms glacier tongues at elevations of 120 metres (390 ft) surrounded by a belt of moraines around the ice edge. Streams draining meltwater have incised glacial deposits. Cliffs with heights of 30–300 metres (98–984 ft) form most of the southern and eastern coasts, while a 18 metres (59 ft) wide youthful coastal terrace makes up the western and northern side. Marine deposits have formed the northward extending Demon Point peninsula, which encloses Kraken Bay between the peninsula and Lucifer Hill. Shrove Point is the southeastern end of Candlemas Island, while Boot Rock juts out from the eastern coastline and Clapmatch and Carbon Points. 750 metres (2,460 ft) east of the coastline is the islet Tomblin Point.