The Pitcairn Reed-warbler (Acrocephalus vaughani) is a songbird in the genus Acrocephalus. Formerly placed in the "Old World warbler" assemblage (Sylviidae), it is now in the newly recognized marsh-warbler family Acrocephalidae.

It is endemic to Pitcairn Island in the southern Pacific. Locally known as the "Sparrow" (true sparrows are not found on Pitcairn), it used to be common throughout the island, where it is the only land bird. It was formerly classified as a Vulnerable species by the IUCN due to its small range. But new research has shown it to be rarer than it was believed. Consequently, it is uplisted to Endangered status in 2008.