The Western Pacific nation of Tuvalu, formerly known as the Ellice Islands, is situated 4,000 kilometers (2,500 mi) northeast of Australia and is approximately halfway between Hawaii and Australia. It lies east-northeast of the Santa Cruz Islands (belonging to the Solomons), southeast of Nauru, south of Kiribati, west of Tokelau, northwest of Samoa and Wallis and Futuna and north of Fiji. It is a very small island country of 26 km² (10 sq mi). Due to the spread out islands it has the 38th largest Exclusive Economic Zone of 749,790 km² (289,500 sq mi).

The Coral reefs of Tuvalu consists of three reef islands and six atolls, containing approximately 710 km² (270 sq mi) of reef platforms. The reef islands have a different structure to the atolls, and are described as reef platforms as they are smaller tabular reef platforms that do not have a salt-water lagoon, although they have a completely closed rim of dry land, with the remnants of a lagoon that has no connection to the open sea or that may be drying up. For example, Niutao has two lakes, which are brackish to saline; and are the degraded lagoon as the result of coral debris filling the lagoon.

The Tuvalu islands have poor soil and a total land area of only about 26 km², less than 10 sq mi (30 km²). The land is very low-lying, with narrow coral atolls. The highest elevation is 4.6 metres (15 ft) above sea level on Niulakita. Over 4 decades, there had been a net increase in land area of the islets of 73.5 ha (2.9%), although the changes are not uniform, with 74% increasing and 27% decreasing in size. The sea level at the Funafuti tide gauge has risen at 3.9 mm per year, which is approximately twice the global average. The rising sea levels are identified as creating an increased transfer of wave energy across reef surfaces, which shifts sand, resulting in accretion to island shorelines, although this process does not result in additional habitable land. but as of March 2018 Enele Sopoaga, the prime minister of Tuvalu, stated that Tuvalu is not expanding and has gained no additional habitable land.

Tuvalu experiences two distinct seasons, a wet season from November to April and a dry season from May to October. Westerly gales and heavy rain are the predominant weather conditions from October to March, the period that is known as Tau-o-lalo, with tropical temperatures moderated by easterly winds from April to November. In terms of size, it is the second-smallest country in Oceania.