Some historians claim that the navigator Pedro Álvares Cabral thought that he had reached this island in 1500, thus naming the country of Brazil. However, Cabral didn't choose the name 'Brazil'. The country was at first named Ilha de Vera Cruz (Island of the True Cross), later Terra de Santa Cruz (Land of the Holy Cross) and still later 'Brazil'. The generally accepted theory states that it was renamed for the brazilwood, which has an extreme red color (so "brasil" derived from "brasa": ember), a plant very valuable in Portuguese commerce and abundant in the new-found land, though it seems far more likely that the Brazilwood was named after the country, which was named afther the mythical island.
Others claimed to have seen the island, or even landed on it, the last supposed sighting being in 1872. Roderick O’Flaherty in A Chorographical Description of West or H-Iar Connaught (1684) tells us "There is now living, Morogh O'Ley, who immagins he was himself personally on O'Brasil for two days, and saw out of it the iles of Aran, Golamhead, Irrosbeghill, and other places of the west continent he was acquainted with."
On maps, the island was shown as being circular, soon with a central strait or river running east-west across its diameter. Despite the failure of attempts to find it, it appeared regularly on maps lying south west of Galway Bay from 1325 until 1865, by which time it was called Brazil Rock.
Jack Vance's Lyonesse Trilogy of fantasy novels is set in the mythical Elder Isles a generation or two before the birth of King Arthur. Situated southwest of Cornwall and west of Brittany, the Elder Isles consist of a large island called Hybras, "the Hy-Brasil of ancient Irish legend," surrounded by numerous smaller islands of various sizes.
In the novel Engelbrecht Again! by Rhys Hughes the main characters meet a mermaid on the (mythical) island of Brasil while on their way to the (real) country of Brazil.
A location in the online game Dragon Court is named Hie-Brasil.
In the Thessaliad (a spin-off of the more popular Sandman comics written by Bill Willingham) a Fetch, or a supernatural bounty hunter, disguised as a taxi driver had his claim to fame by hunting down all thirty-nine forgotten gods of Hy Brasil.
Hy Brasail is a Lost Ground in the .hack Conglomerate. It is a Lost Ground only accessible during official events. The island lies right outside the harbor of Mac Anu, and the skyline of the city can be seen from its shores.