The first signs of human habitation date from the Paleolithic, in form of primitive tools.
 Sporadic remnants from the Neolithic age have been found in the neighbouring areas.

During the wars between Romans and Dacians, the Bistra Valley was the route used by the emperor Trajan in penetrating into the heartland of Dacia.
 A Roman castrum can be found near the cemetery of Zăvoi (ancient Agnaviae), a settlement close to Oțelu Roșu.

In the fifteenth century, during medieval times, Oțelu Roșu was mentioned under the name of "Bistra", and later with the Hungarian name of Nándorhegy.
After the expulsion of Turks from Banat by the Habsburgs, the area was colonised by Germans.
Also, Italians are brought in to work in metalworking industry.
Within the Kingdom of Hungary, the town was part of Krassó-Szörény County from 1881 to 1920.
Later, as the northeastern part of the Banat became part of Romania following the Treaty of Trianon in 1920, the name of Nándorhegy was replaced with Ferdinand.

After 1947 the name Ferdinand did not please the Socialist Republic of Romania government, who changed it to Oțelu Roșu ("[The] Red Steel") in order to underline the importance of the town's metalworking industry.
The first signs of human habitation date from the Paleolithic, in form of primitive tools.  Sporadic remnants from the Neolithic age have been found in the neighbouring areas.
During the wars between Romans and Dacians, the Bistra Valley was the route used by the emperor Trajan in penetrating into the heartland of Dacia.  A Roman castrum can be found near the cemetery of Zăvoi (ancient Agnaviae), a settlement close to Oțelu Roșu.
In the fifteenth century, during medieval times, Oțelu Roșu was mentioned under the name of "Bistra", and later with the Hungarian name of Nándorhegy. After the expulsion of Turks from Banat by the Habsburgs, the area was colonised by Germans. Also, Italians are brought in to work in metalworking industry. Within the Kingdom of Hungary, the town was part of Krassó-Szörény County from 1881 to 1920. Later, as the northeastern part of the Banat became part of Romania following the Treaty of Trianon in 1920, the name of Nándorhegy was replaced with Ferdinand.
After 1947 the name Ferdinand did not please the Socialist Republic of Romania government, who changed it to Oțelu Roșu ("[The] Red Steel") in order to underline the importance of the town's metalworking industry.
Oțelu Roșu