Phillip Island is an uninhabited island located 6 km (3.7 mi) south of Norfolk Island in the Southwest Pacific, and part of the Norfolk Island group. It was named in 1788 by Lieutenant Philip Gidley King for Arthur Phillip, the first Governor of New South Wales. It is part of the Australian territory of Norfolk Island. It is included in Norfolk Island National Park, as is neighbouring Nepean Island, and about 10 per cent of Norfolk Island proper. Phillip Island has an area of 190 hectares (470 acres), measuring 2.1 km (1.3 mi) from west to east and 1.95 km (1.21 mi) from north to south, with the highest point, Jacky Jacky, 280 m (920 ft) above sea level. It is roughly shaped like a hairdryer with the nozzle pointing east. The island is of volcanic origin, made of basaltic tuff and lava dating from the Miocene epoch. Phillip Island is included on the Register of the National Estate.
The vegetation of Phillip Island was devastated due to the introduction, during Norfolk's penal colony era, of pest animals such as pigs, goats and rabbits. This caused massive erosion, giving the island a reddish-brown colour as viewed from Norfolk, due to the absence of topsoil. However, the pigs and goats were removed by the early 20th century, and rabbits were exterminated by 1988. Since then, natural regeneration of native species and weeds, and remediation work by park staff, has brought considerable improvement to Phillip Island's environment. Revegetation is currently underway. A substantial proportion of the areas which were bare before rabbit eradication began is now well vegetated, though much is weed species. Considering most of the island's surface was completely devoid of vegetation before rabbit control, the rate of vegetation development and soil formation is extraordinary. Burrow-nesting seabirds now have colonies where soil was absent before rabbit eradication. Reforestation of Norfolk Island pine on Phillip was assisted in the late 1980s by a C130E Hercules from 37 Sqn RAAF Richmond. Record crops of Norfolk pine seeds were collected and aerial seeded on Phillip Island by the Hercules aircraft. Phillip island has a vascular flora of about 80 species. Three plant species are endemic to Phillip Island. (Achyranthes margaretarum) was discovered there after the rabbits had gone, and the current small population of this species is derived from the single original plant discovered. (Abutilon julianae) was rediscovered on Phillip Island when the rabbits had almost been eradicated; it had been believed extinct for more than seventy years. The third plant that grows only on this island is the (Hibiscus insularis).