Drain the Swamp Act of 2021 This bill repeals the requirement that all offices attached to the seat of the federal government be exercised in the District of Columbia, except as otherwise expressly provided by law. Each executive agency, by September 30, 2022, must submit a plan for the relocation of its headquarters outside of the Washington metropolitan area. Such plan shall identify a location for a new headquarters; maximize any potential cost savings associated with the relocation; provide that, upon implementation of the plan, no more than 10% of agency employees are based in the Washington metropolitan area; and consider any potential national security implications of the relocation. Each agency shall implement the plan by September 30, 2026.