Papilio demoleus Linnaeus, 1758 (Lepidoptera: Papilionidae) is a widespread pest of citrus plants originating from the Oriental Region. Here, we report on the discovery of its non-native population recently established on Mahé, Seychelles. Papilio demoleus was probably accidentally introduced to Mahé a few years ago (first records in November 2016). Morphologically, the Seychelles population is identified as the subspecies Papilio demoleus malayanus Wallace, 1865 from Southeast Asia. It was one of the most abundant butterfly species at the southeastern edge of Mahé in January 2020. Our finding highlights that generalist butterfly species associated with agricultural plants are rapidly spreading throughout remote oceanic islands such as the Inner Seychelles.