The Mascarene White-eye (Zosterops borbonicus), also known as Grey White-eye, is a small passerine from the family Zosteropidae, which is endemic to the islands of Mauritius and Réunion.
The taxon mauritianus, by most authorities considered a subspecies of the Mascarene White-eye, has occasionally been considered a separate monotypic species, the Mauritius Grey White-eye (Zosterops mauritianus), in which case the common name of the remaining species often is modified to Réunion Grey White-eye. There is some uncertainty about the number of subspecies on Réunion, with most authorities only accepting a single, the nominate (Z. b. borbonicus), while some also accept Z. b. alopekion, and Z. b. xerophilus. When only a single Réunion subspecies is accepted, alopekion and xerophilus are considered to represent morphs of the nominate.
It has a length of 9.5 cm. Its plumage exhibits a colour morph which varies from gray to brown. The rump is coloured conspicuous white, the rest of the body is blue grey. The legs are nearly blackish. There is also a conspicuous ring of white feathers around the chestnut coloured eyes.
In Mauritius, it shares its habitat with the Mauritius Olive White-eye (Zosterops chloronotus). It inhabits woodlands, forests, and gardens. It is the only endemic bird from Réunion and Mauritius which has adapted to man-made conditions. Its diet consists of insects, fruits and nectar. It is also the pollinator for orchids like Angraecum striatum or the endemic Trochetia species. It moves often in small groups from six to twenty birds in search of food. They are very noisy. The breeding period is in the southern summer. The female lays two to four pale blue eggs in a cup-shaped nest which is padded with plant material.