A protective sheath for cables, particularly industrial cables of great dimensions and weight used in port and similar installations that is structured in an inner layer (1) that keeps the cables arranged together inside it and constitutes for them the first insulation； an inner sheath (2) that is of fireproof material and is attached to the inner layer (1) both forming a primary insulation. An armour (3) made of light and resistant material, that envelops the inner sheath and inner layer, resists high temperatures and provides it with a high degree of protection against fire and great rigidity to the assembled unit； an outer sheath (4) that constitutes a covering, also of fireproof material； so that in the joint performance of the four layers and sheaths the sheath is provided protection against fire for at least 20 minutes.
