Mount Penang Juvenile Justice Centre, Heritage-listed detention center in Somersby, Australia

Mount Penang Juvenile Justice Centre is a heritage-listed former detention centre on the Pacific Highway at Somersby, designed by James Nangle and built from 1912 by the NSW Public Works Department. Its earliest buildings resemble lighthouse cottages, and the site now operates as Mount Penang Parklands with parks, a high school, an events park, offices and housing.

Opened in 1912 as The Farm Home for Boys, the centre was designed by James Nangle and built by the New South Wales Public Works Department, with inmates providing labour for major buildings until 1922. It later became Girrakool and Kariong Juvenile Detention Centre, holding 170 boys, the largest such centre in the Southern Hemisphere. It was added to the New South Wales State Heritage Register in September 2003.

The name Kariong comes from an Aboriginal word said to mean "meeting place", and the site lies on Darkinjung language-group land. A 1994 Aboriginal sites study recorded rock engravings, grinding grooves and shelters with art and occupation deposits on the Hawkesbury Sandstone here, with motifs of kangaroos, whales, fish and eels.

Mount Penang Parklands sits on the Pacific Highway at Somersby, about 60 km north of Sydney on the Central Coast. The former detention centre buildings stand within the parkland precinct, alongside a high school, an events park and commercial and office space. Visitors can walk between the heritage buildings and the surrounding parks and gardens; the site is on the Darkinjung traditional lands, and the 1994 Aboriginal sites study recorded rock engravings, grinding grooves and shelters in the Hawkesbury Sandstone formations.

The earliest buildings, put up between 1912 and 1922, were raised by the inmates' own labour, and several are still in use. Some were designed to look like lighthouse cottages, a nod to the reform school's origins aboard retired navy ships in Sydney Harbour.