Gas giant
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope.
Outline of Nauru
Nauru – sovereign island nation located in the Micronesian South Pacific. Its nearest neighbour is Banaba Island in the Republic of Kiribati, due east. Nauru is the world's smallest island nation, covering just , the smallest independent republic, and the only republican state in the world without an official capital. It is the least populous member of the United Nations.