Corrugated galvanised iron or steel occasionally is a building material composed of sheets of hot-dip galvanised mild stel, cold-rolled to produce a linear corrugated pattern in them. The corrugations increase the bending strength of the sheet in the direction perpendicular to the corrugations, but not parallel to them. Normally each sheet is manufactured longer in its strong direction .

Wrought iron CGI was gradually replaced bymild steel from around the 1890s, and iron CGI is no longer obtainable but the common name has not been changed. Galvanized sheets with simple corrugations are also being gradually displaced by 55% Al-Zn coated steel[5] orcoil-painted sheets with complex profiles. CGI remains common.
CGI is lightweight and easily transported. It was and still is widely used especially in rural and military buildings such as sheds and water tanks. Its unique properties were used in the development of countries like Australia from the 1840s, and it is still helping developing countries today.