SCHEDULE 13G

First Interstate BancSystem Inc

Common Stock · CUSIP: 32055Y201

Event date: 2025-09-30

Reporting persons may disclose overlapping interests. Their amounts are shown individually and are not added into a filing total.

Filing-level shares

Unavailable

Percent of class

Unavailable

• Wellington Management Group LLP

  Shares: 5,915,425.00 · Class: 5.6%

• Wellington Group Holdings LLP

  Shares: 5,915,425.00 · Class: 5.6%

• Wellington Investment Advisors Holdings LLP

  Shares: 5,915,425.00 · Class: 5.6%

• Wellington Management Company LLP

  Shares: 5,915,425.00 · Class: 5.4%

Amounts are as disclosed in this filing. Schedule type alone does not establish investment intent.