Revive Economic Growth and Reclaim Orphaned Wells Act of 2021 or the REGROW Act of 2021 This bill provides funding for grants to plug orphaned (i.e., abandoned) oil and gas wells, clean up pollution leaking from such wells, and conduct research and related activities. Specifically, the bill provides funding for a grant program within the Department of the Interior to plug and clean up orphaned wells located on federal, state, tribal, and private land. In addition, the bill provides funding to the Department of Energy and the Oil and Gas Compact Commission for conducting research and development activities to assist federal land management agencies, states, and Indian tribes in (1) identifying and characterizing undocumented orphaned wells, and (2) mitigating the environmental risks of undocumented orphaned wells.