Avista Corporation is an American energy company. Avista generates and transmits electricity and distributes natural gas to residential, commercial, and industrial customers. Approximately 1,550 employees provides electricity, natural gas, and other energy services to 359,000 electric and 320,000 natural gas customers in three western states. The service territory covers 30,000 square miles (78,000 km) in eastern Washington, northern Idaho, and parts of southern and eastern Oregon, with a population of 1.5 million.

Avista Utilities is the regulated business unit of Avista Corp., an investor-owned corporation headquartered in Spokane, Washington. Avista Corp.'s primary, non-utility subsidiary was Ecova, an energy and sustainability management company with over 700 expense management customers, representing more than 600,000 sites. In 2014, Ecova was sold to Cofely, a subsidiary of GDF Suez.

The company was founded in 1889 as Washington Water Power Company. The board of directors approved a name change to Avista Corporation, effective January 1, 1999. The company began trading under the Avista name on January 4, 1999.

At that time, the company also bought naming rights for Spokane's minor league baseball park, Avista Stadium.

Washington Water Power was founded in 1889 helping the new and booming city of Spokane Falls to have more power. Using the Spokane River, the idea was that the town could use water power. Trustees of the Edison Electric Illuminating Company asked for people to back them up in their project from New York to build a power station on the river. The people in New York refused saying that water power had little to no value. Defying the people in New York, 10 stockholders stepped up to support the project themselves and formed Washington Water Power to build it.

Washington Water Power expanded in Oregon and into California by acquiring the natural gas operations of CP National from Alltel in 1989. The California operations were sold to Southwest Gas in 2005.

In 2014, Avista acquired Alaska Electric Light & Power, the electric utility for Juneau.

In 2017, Ontario-based electrical utility Hydro One agreed to purchase Avista. The newly combined company will have a 30 year lease on Ontario's public electricity distribution assets.

On September 27, 2002, Avista was sued for issuing false and misleading statements concerning its business and financial condition, including failing to disclose that Avista was engaged in highly risky energy trading activities with Enron and Portland General Electric. On December 20, 2007, Avista agreed to a $9.5 million settlement.

On February 20, 2002, the company had voluntarily adjusted the amount originally allocated to IPR&D and will restate its third quarter 1998 consolidated financial statements accordingly.