The town is bounded on the south by the namesake Junk Bay, known as Tseung Kwan O () in Chinese. Most of the residential developments in the new town stand on land reclaimed from the bay. The mountains of Devil's Peak, Chiu Keng Wan Shan, Black Hill and Tai Sheung Tok form the new town's western boundary, where it borders Kwun Tong District of Kowloon. Lying to the north and southeast of the town are Razor Hill and High Junk Peak, which separate the new town from the rural parts of Sai Kung District.