We present compelling evidence of the continued existence of the large-billed reed warbler Acrocephalus orinus, hitherto known only from the unique type specimen collected in NW India 139 years ago. Morphological and genetic analyses of an unusual Acrocephalus warbler mist-netted south-west of Bangkok, Thailand, on 27 March 2006, confirmed its identity as A. orinus, and revealed that it was heterozygous at four out of eight microsatellite markers, indicating the continued existence of a viable population whose breeding and wintering areas are still unknown.