Monarch Action, Recovery, and Conservation of Habitat Act of 2021 or the MONARCH Act of 2021 This bill provides support for the conservation of western monarch butterflies (the monarch butterfly population that overwinters along the coast of California and breeds across California, Arizona, Nevada, Washington, Oregon, Idaho, and Utah). Specifically, the bill establishes the Western Monarch Butterfly Rescue Fund. The Department of the Interior must use amounts in the fund to provide grants for the conservation of such butterflies. In addition, Interior must enter into an agreement with the National Fish and Wildlife Foundation to facilitate the implementation of the Western Monarch Butterfly Conservation Plan, which was prepared by the Western Association of Fish and Wildlife Agencies.