Tren de las Nubes (Spanish for Train of the Clouds) is a train service in Salta Province, Argentina, that connects the Argentine Northwest with the border with Chile in the Andes mountain range, over 4,000 meters above mean sea level, the third highest railway in the world. Originally built for economic and social reasons, it is now of primarily touristic value as a heritage railway.

The train leaves Wednesdays, Fridays and Sundays at 7:05am from General Belgrano station in the city of Salta for the 15 hour-, 434 kilometre round trip to the viaduct La Polvorilla, located 4,220 meters above sea level. The curved viaduct is 224 meters long and 70 meters high. From Salta, the train enters first the Valle de Lerma and then the Quebrada del Toro before reaching the Puna. It is known as the Train to the Clouds because clouds can be often be seen around and under the bridges and slopes of the landscape through which the railway passes.