The Phillip Island Grand Prix Circuit is a motor racing circuit located near Ventnor, on Phillip Island, Victoria, Australia. The current circuit was first used in 1952.

Along with The Bend Motorsport Park in South Australia, the 4.448 km (2.764 mi) long island circuit is one of two race tracks in Australia to carry a FIM Category A track licence which allows for the highest level of motorcycle racing, MotoGP. Phillip Island also carries an FIA Grade 3 track licence.

Motor racing on Phillip Island began in 1928 with the running of the 100 Miles Road Race, an event which has since become known as the first Australian Grand Prix. It utilised a high speed rectangle of local closed-off public roads with four similar right hand corners. The course length varied, with the car course approximately 6 mi (9.7 km) per lap, compared to the motorcycle circuit which was approximately 10 mi (16 km) in length. The circuit was the venue for the Australian Grand Prix through to 1935 and it was used for the last time on 6 May 1935 for the Jubilee Day Races.

A new 3.312 mi (5.330 km) triangular circuit utilising the pit straight from the original rectangular course was subsequently mapped out and first used for the Australian Race Drivers' Cup on 5 November 1935. The final car event on the circuit was held on Cup Day (1 November) 1938 and the final motorcycle race meeting was conducted on 30 January 1940.

Significant events staged at the Phillip Island road circuit included:

In 1951, a group of six local businessmen decided to build a new track. About 2 km (1.2 mi) away from the original circuit, it still bears the corner name signs of the original circuit. As the piece of available land was on the edge of the coast, the track is known for its steep grades – the highest 57 metres – which caused cost overruns and delays in track opening. The new track was opened in 1952 and in 1960 the first Armstrong 500 production car race was held at the circuit. Extensive damage resulted from the running of the 1962 Armstrong 500, and, with the circuit owners unable to finance repairs, the circuit was closed and the race was moved to the Mount Panorama Circuit at Bathurst in New South Wales, to eventually become known as the Bathurst 1000.

The circuit reopened in October 1967 and hosted the Phillip Island 500 endurance race, a round of the Australian Manufacturers' Championship, from 1971 to 1977. The race was also a round of the Australian Touring Car Championship in 1976 and 1977. But again, due to its testing terrain, the circuit required significant maintenance and slowly declined through the 1970s. It was farmed by its owners while closed and was then sold in 1985 in preparation for reopening, but did not do so until 1988 after agreement on a long-term lease and rebuild agreement. During the time the circuit deteriorated and finally closed, part of the main problem for its owners was that the Phillip Island Bridge from the island to the Australian mainland reportedly could not carry the heavy vehicles needed to resurface the circuit. This meant that the bitumen surface was a cold mix which easily broke up under the rigours of racing, instead of the standard hot mix which would have allowed a more durable surface. It would not be until the mid-1980s that the bridge would be rebuilt allowing the necessary equipment needed for resurfacing.

The circuit was refurbished with a reduced length of 4.448 km (2.764 mi) and was reopened on 4 December 1988 for the final round of the 1988 Swann Insurance International Series for motorcycles.