This is a list of tallest freestanding steel structures in the world past and present.
To be a freestanding steel structure it must not be supported by guy wires, the list therefore does not include guyed masts and the main vertical and lateral structural elements and floor systems in the case of buildings, are constructed from steel.
This type of construction is a rarity today as most tall buildings are built with a composite structure featuring a reinforced concrete core.
Oil platforms built using rigid steel jackets, such as the Bullwinkle (oil platform), are included and ranked as the local medium(water) does not provide any horizontal support.
In fact they are over engineered specifically to resist water forces them rather than modulate them as compliant towers are designed to do.