The Ma On Shan line (Chinese: 馬鞍山綫) was a commuter rail / rapid transit line that formed part of the Mass Transit Railway (MTR) system in Hong Kong.

It was reported that some bus routes operated by KMB saw a decrease of ridership by one-third in just a few days.

Under Phase 1 the Sha Tin to Central Link project, the Ma On Shan line would be extended from Tai Wai station to Hung Hom station via East Kowloon, with six new intermediate stations, including interchanges with the Kwun Tong line at Diamond Hill and Ho Man Tin, an additional interchange with the East Rail line at Hung Hom, and a new station, Hin Keng, serving Sha Tin.

The extension will connect to the West Rail line at Hung Hom and continue on to Tuen Mun station in the northwest New Territories via the current West Rail line and its 2009 extension to Hung Hom).

Due to various delays, the new line opened only as far as Kai Tak on 14 February 2020, with the remaining section to Hung Hom to begin service on 27 June 2021.