Castle Hill is a heritage-listed isolated pink granite monolith in the suburb of Castle Hill, City of Townsville, Queensland, Australia. It rises to a height of some 286 metres (938 ft) above sea level and dominates the city skyline. It is one of the most distinctive natural features on the Queensland coast. There are a number of vantage points from which to view the city below and also across Cleveland Bay to nearby Magnetic Island. Castle Hill (as a hill) was listed on the Queensland Heritage Register in 1993.
The hill is an inselberg of Carboniferous–Permian origins, rising abruptly from the younger Quaternary coastal plain. The surface is primarily bare rock or shallow lithsols with small areas of duplex soils. There are three peaks to the summit. There is a former quarry site on the southern slopes, accessed via Stagpole Street, and on the northern cliff face a large graffiti on 'The Saint' is painted.
The bitumen "Castle Hill Road" winds for 2.6 kilometres from the northeast slopes to the summit of the second peak, on which the Hynes Lookout platform has been erected.
There are several buildings and installations on the hill. On the southern face was a two-storeyed octagonal building of concrete block work, which formerly housed the Panorama Restaurant, which has now been demolished. A carpark associated with the former restaurant is located nearby to the north. Other structures on the site include several water reservoirs and three radio communication installations. On the northern-most peak of the summit is a 1942 observation post, a low, square, concrete bunker with observation apertures.
In 1873, Robert Towns, the founder of Townsville, died in Sydney and was buried in Balmain Cemetery.