The water‐gas shift (WGS) reaction is the exothermic conversion of carbon monoxide and water to hydrogen and carbon dioxide. The reaction is of industrial importance for purification when traces of carbon monoxide have to be removed from gaseous feed, such as in the Haber—Bosch process for ammonia production or in modern polymer electrolyte membrane (PEM) fuel cells. Modern WGS catalysts are divided into four classes: HTS, LTS, sour gas shift, and precious‐metal‐containing catalysts. The development of a supported IL catalysts system involves a work strategy similar to a development in heterogeneous catalysis. The use of homogeneous transition‐metal complexes for the important WGS reaction has been investigated during the past decades in both academia and industry. It can be anticipated that supported ionic liquid phase (SILP) catalysts will be implemented in ultralow temperature WGS processes in the near future.