New Guanjiao Tunnel

New Guanjiao Tunnel is a tunnel on the 2nd line of Qinghai–Tibet Railway in Guanjiao Mountain, Qinghai province. It is dual-bored, double-track rail tunnel. The total length of the tunnel is 32.645 km, which made it at the time of completion the longest railway tunnel in China and fourth-longest in the world.

China Railway First Survey and Design Institute is responsible for the design. The New Guanjiao Tunnel was designed for two parallel single-track tunnels with speeds of up to 160 kph. The total construction duration was projected to be 5 years. The tunnel was bored in difficult geological conditions and high altitude, exceeding 3300 m above sea level. The construction started in 2007 and was completed in April 2014. The tunnel was opened on 28 December 2014.

The tunnel's northeastern portal (37.1834°N, 99.1778°W) is in Tianjun County, the southwestern portal (37.0094°N, 98.8805°W) is in Ulan County.