The Chestnut-sided White-eye (Zosterops mayottensis) is a species of bird in the Zosteropidae family. It is now found only on Mayotte in the Comoro Islands. Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist lowland forests, and subtropical or tropical mangrove forests.
The subspecies semiflava (Seychelles Chestnut-sided White-eye) formerly occurred on Marianne and perhaps other islands in the Seychelles but is now extinct. It may be better classified as a separate species.