Luggnagg is an island that possesses a unique group of inhabitants that claim to be immortal.
When Gulliver journeys to Luggnagg attempting to pose as a Dutchman, his ruse is discovered, and he is incarcerated. The Luggnaggian King sends for Gulliver, and we then learn about the King's many idiosyncrasies. He requires those who come before him to approach on their hands and knees and to lick the floor. When someone falls out of favor with the King, he applies poison the floor they are to lick. Gulliver follows the King's eccentric customs, and because he is willing to submit to the questions posed to him, Gulliver is invited to stay as a guest of the royal court for three months.
Gulliver hears about the Struldbruggs during his stay, a group of people in Luggnaggian society who are apparently immortal. Gulliver reacts at first with excitement and envy, as this power would allow a person plenty of time to amass great knowledge, and gain immense wealth. His fantasies are crushed, however, when an interpreter proceeds to explain the reality of life as a Struldbrugg. When Gulliver realizes that they still continue to grow old, feeble, decaying, and forgetful, his desire for this life of immortality disappears as quickly as it had formed.
Luggnagg also trades with Japan to the northwest from its port at the southwestern part of the island, Glanguenstald.
- Traldragdubb or Trildrogdrib, the capital city of Luggnagg.
- Clumegnig, a port city on the southeast coast that trades with Maldonada of Balnibarbi.
- Glanguenstald, a port city on the southwest coast that trades with Japan.
- A mythical island known as Mount Penglai (Chinese: 蓬莱仙岛, Pénglái xiāndǎo; Japanese: 蓬莱, Hōrai) exists in Chinese and Japanese mythology, with four other islands located near Mount Penglai. While the Chinese consider it to be the fantastic realm of the Eight Immortals, the Japanese considered it to be a less pleasant realm inhabited by a sky of ancient souls and tiny innocent fairies. The Japanese also considered Mount Penglai to be more of a fantasy.
- Gulliver found that the Luggnaggian language was rather unpleasant to his ears.
- Luggnagg's name in the Japanese language is "ラグナグ" (Ragunagu), reflecting the English pronunciation of the name.