Great Western Bank, whose holding company was Great Western Bancorp, Inc. (NYSE: GWB), was a regional bank based in Sioux Falls, South Dakota, United States.

In September of 2021 they announced a merger with First Interstate BancSystem and completed it in February of the following year.

In October 2014, NAB began to release its holding through an initial public offering.

[6] In November 2015, Great Western announced the acquisition of Sioux Falls-based HF Financial Corp., the parent company of Home Federal Bank.

[7] In 2021, Great Western Bank signed a definitive agreement to merge with Montana-based First Interstate BancSystem.