Dali–Ruili railway or Darui railway (simplified Chinese: 大瑞铁路; traditional Chinese: 大瑞鐵路; pinyin: dàruì tiělù), is a single-track electrified railroad under construction in Yunnan Province of Southwest China. The line is slated to run 336.39 km (209 mi) from Dali in central Yunnan to Ruili in southwestern Yunnan on the border with Myanmar. The line traverses rugged terrain, and bridges and tunnels will account for 75% of the total track length, including the 36 km Gaoligongshan Tunnel through the Gaoligong Mountains. Construction began in May 2011 and was scheduled to take six years. However, this has been repeatedly delayed, and as of 2019 the railway is scheduled to open only in 2022. Cities and towns along route include Dali, Yangbi Yi Autonomous County, Yongping County, Baoshan, Mangshi and Ruili.
As early as 1938, the British planned to build the Yunnan–Burma railway to connect British rule in Burma with Yunnan Province, but were unable to complete the project.
Originally, the Chinese government proposed a rail connection between Kunming, China and Kyaukpyu, Myanmar. The railway was planned to follow the route of the existing Sino-Myanmar pipelines. After protests in Myanmar, the part of the railway in Myanmar was cancelled. Only the Chinese part of the line between Dali and Ruili will now be constructed.
Construction on the Darui Line began in 2008. In August 2012, the project received an additional investment of ¥5 billion, owing to the difficulty of tunneling through the rugged terrain. The huge rivers and geology have given the corridor the monikor World’s Most Difficult Railway.
The Dali–Ruili railway may some day form the western route of China’s rail link with Southeast Asia, part of the Trans-Asian Railway. The authorities of the two countries considered the possibility of connecting it with the railways of Myanmar. In 2018, another agreement was signed between the two countries’ railway agencies for a feasibility study for a 431 km long railway connection from Mandalay to Muse (the Burmese town opposite Ruili).