Welding gas refers to gases used in the welding process to shield the weld area from atmospheric contamination and to provide certain desirable properties to the weld. These gases are typically used in welding methods such as gas metal arc welding (GMAW) or gas tungsten arc welding (GTAW), also known as MIG (Metal Inert Gas) welding and TIG (Tungsten Inert Gas) welding, respectively.

The most commonly used welding gas is a mixture of argon and carbon dioxide, commonly known as MIG welding gas or shielding gas. This mixture provides an inert atmosphere around the weld, preventing the molten metal from reacting with oxygen and other elements in the air, which can cause defects and impurities in the weld.