The Kwun Tong line is a rapid transit line of the MTR network in Hong Kong, coloured green on the MTR map. Starting at Whampoa in Hung Hom and ending at Tiu Keng Leng in Tseung Kwan O, Sai Kung, the route has 17 stations and takes 35 minutes to complete. The Kwun Tong line is one of the busiest railway lines on the network connecting the central and the eastern portions of Kowloon via Wong Tai Sin. The line is mostly underground, but includes a lengthy elevated section, and runs generally in an east-west direction. During the morning rush hour, the Kwun Tong line utilises 33 trains running at 29tph to achieve a route capacity of 85,000 pphpd.

The East Rail line is one of the ten lines that form MTR, the mass transit system in Hong Kong. The railway line starts at Lo Wu or Lok Ma Chau, both of which are boundary crossing points into Shenzhen and joins in the north at Sheung Shui and ends at Admiralty station on Hong Kong Island. At approximately 46 km (29 mi), the line is the second longest line within the network, behind the Tuen Ma line. The line's colour is light blue, formerly navy blue before the KCR/MTR merger.