Obsidian Skin Potion

The Obsidian Skin Potion is a buff potion which buffs the player with Obsidian Skin. The buff grants immunity to lava, Hellstone and Meteorite for 4 minutes (but can be cancelled at any time by right-clicking the icon). You can, however, still drown in lava.

A Water Walking Potion is a viable alternative to an Obsidian Skin Potion for some purposes, as it will allow you to stand on the surface of lava without taking damage.