This is the 27th Lead Inspector General (Lead IG) report to the United States Congress on Operation Inherent Resolve (OIR), the overseas contingency operation to combat the Islamic State in Iraq and Syria (ISIS). The report covers the period July 1, 2021 – September 30, 2021, summarizes the quarter’s key events and describes completed, ongoing, and planned Lead IG and partner agency oversight work related to OIR.