thumb|257x257px|Map of the island
thumb|257x257px|The flag of Swains Island was described as "[[Old Glory [...] but superimposed on the blue field was a white dove" At the 2023 celebration marking the 98th anniversary of Swains Island being joined with America Samoa, the Swains Island flag was raised alongside the U.S. and American Samoan flags in Taulaga Village.]]
Swains Island (; ; ), also known as Jennings Island, is a remote coral atoll in the Tokelau volcanic island group in the South Pacific Ocean. Administered as part of American Samoa since 1925, the island is subject to an ongoing territorial dispute between Tokelau and the United States. Swains Island was used as a copra plantation until 1967.
The island is located south of Fakaofo (Tokelau) and north of Savai‘i (Samoa). The land area is ,
Swains Island was long believed to have been first charted on 2 March 1606 by Pedro Fernandes de Queirós, a Portuguese navigator who sailed for Spain. On that date, he reckoned an island at 10°36′S 171°W, and his ship's historian named it (Spanish for 'island of the beautiful people'), after its inhabitants. The closest island to that reckoned location is Swains Island at , leading later authors to label it with the Spanish name or the Spanish version of Queirós's surname, Quirós. However, the island described by Queirós was significantly larger and, considering likely errors in the calculation of longitude, later scholars concluded that the island found by Queirós was actually Rakahanga, lying to the east.
This Captain Swain has not been conclusively identified. Authors have suggested it might be Jonathan Swain of whaler Independence in 1820, Other evidence suggests Obed Swain of whaler Jefferson of Nantucket, who was at Tahiti when the United States Exploring Expedition was there with the USS Peacock.
It is also called Jennings Island, after Eli Hutchinson Jennings, who settled there in 1856 and whose family still owns and manages the island.
In Tokelauan, the main language formerly spoken on Swains Island, the island is called . The name is composed of the prefix , indicating a collective noun, and the word , meaning a tuft of feathers tied to the end of a skipjack lure, possibly referring to the island's location at the end of the Tokelau chain. A variant of this name is in both Tokelauan and Samoan.
The atoll is somewhat unusual, featuring an unbroken circle of land enclosing a lagoon separated from the sea. The channel connecting the lagoon to the sea likely closed around . The lagoon has a maximum depth of and contains significant amounts of algae and two species of freshwater fish. A 1998 investigation of the lagoon noted possible evidence that the lagoon is fed by volcanic springs; fresh water plumes were also noted in the island's fringing reef. Nearly all of the land is filled with coconut palms.
Swains Island is part of the National Marine Sanctuary of American Samoa. The Swains Island sanctuary area encompasses a and includes territorial waters within a circle around the island, excluding the interior lagoon and two channels between the lagoon and the sea. Like other areas of its coastline, the United States claims a exclusive economic zone around Swains Island, making up about a third of the U.S. EEZ in the South Pacific.
Fauna
thumb|Bigeye trevally (Caranx sexfasciatus) on the reef around Swains Island in 2012.
The island has been recognised as an Important Bird Area (IBA) by BirdLife International because it supports a breeding population of white terns. Seven reptile species have been recorded from the island, including three geckos and three skinks, as well as the green sea turtles which formerly nested on the island, but now occur only as visitors to inshore waters. A 2012 survey noted the island's seabird community was dominated by black noddies, white terns, and brown noddies, while the reef flat was dominated by Pacific golden plovers and wandering tattlers. Inland surveys found roosting or breeding communities of noddys, terns, and red-footed boobies. The island is also home to coconut crabs, as well as several non-native invasive species, including Pacific rats and feral cats. Feral pigs were eradicated from the island in the early 2010s. In 2022, the American Samoa Department of Marine and Wildlife Resources received a grant to help eradicate non-native predators from Swains Island.
In the lagoon, two freshwater fish were reported as common in 2013: a goby and a molly; however, the specific species were unidentified. Predator species, such as barracudas, jacks, and snappers, are also found near Swains Island, and sharks and humphead wrasse are frequently seen in its nearshore waters. Dogtooth tuna is more common near Swains than other waters of American Samoa.