California Water Service Group (CWSG) is an American public utility company providing drinking water and wastewater services.

It is the third-largest investor-owned publicly-traded water utility in the United States, serving roughly two million people through its subsidiary companies in California, Hawaii, New Mexico and Washington.

[1] CWSG was formed in 1997 as a new holding company for California Water Service to expand into other states regulated by their own public utilities commissions, and into other non-regulated businesses.

In 1998, CWSGs original subsidiary, California Water Service, made a major expansion into Southern California with the purchase of Dominguez Services Corp. for $53 million, incorporating its subsidiaries Antelope Valley Water Co. and Kern River Valley Water Co. into Cal Water's service districts.

[2] In 2002, CWSG acquired Rio Grande Utility Corporation to form its New Mexico Water Service subsidiary.