The Réunion ibis or Réunion sacred ibis (Threskiornis solitarius) is an extinct species of ibis that was endemic to the volcanic island of Réunion in the Indian Ocean. The first subfossil remains were found in 1974, and the ibis was first scientifically described in 1987. Its closest relatives are the Malagasy sacred ibis, the African sacred ibis, and the straw-necked ibis. Travellers' accounts from the 17th and 18th centuries described a white bird on Réunion that flew with difficulty and preferred solitude, which was subsequently referred to as the "Réunion solitaire".
In the mid 19th century, the old travellers' accounts were incorrectly assumed to refer to white relatives of the dodo, due to one account specifically mentioning dodos on the island, and because 17th-century paintings of white dodos had recently surfaced. However, no fossils referable to dodo-like birds were ever found on Réunion, and it was later questioned whether the paintings had anything to do with the island. Other identities were suggested as well, based only on speculations. In the late 20th century, the discovery of ibis subfossils led to the idea that the old accounts actually referred to an ibis species instead. The idea that the "solitaire" and the subfossil ibis are identical was met with limited dissent, but is now widely accepted.
