The Trans Siberian Railway-Line. The Longest?

No. The T.S. R. is a network.

The Trans-Siberian Railway or Trans-Siberian Railroad (Транссибирская магистраль, Транссиб in Russian, or Transsibirskaya magistral', Transsib) is a network of railways connecting Moscow and European Russia with the Russian Far East provinces, Mongolia, China and the Sea of Japan. The Trans-Siberian railway is often associated with the main transcontinental Russian train that connects hundreds of big and small cities of the European and Asian parts of Russia. At 9,288 kilometres (5,772 miles), spanning a record 15 time zones and taking several days to complete the journey, it is the third-longest single continuous service in the world, after the Moscow–Pyongyang (10267 km, 6380 mi) [1] and the Kiev–Vladivostok (11085 km, 6888 mi) [2] services, both of which also follow the Trans-Siberian for much of their routes. The route was opened by Tsarevich Nicholas Alexandrovitch of Russia after his eastern journey ended.