Transportation, Housing and Urban Development, and Related Agencies Appropriations Act, 2021 This bill provides FY2021 appropriations to the Department of Transportation (DOT), the Department of Housing and Urban Development (HUD), and several related agencies. The bill provides appropriations to DOT for the Office of the Secretary, the Federal Aviation Administration, the Federal Highway Administration, the Federal Motor Carrier Safety Administration, the National Highway Traffic Safety Administration, the Federal Railroad Administration, the Federal Transit Administration, the Saint Lawrence Seaway Development Corporation, the Maritime Administration, the Pipeline and Hazardous Materials Safety Administration, and the Office of Inspector General. The bill provides appropriations to HUD for Management and Administration, Public and Indian Housing, Community Planning and Development, Housing Programs, the Federal Housing Administration, the Government National Mortgage Association (Ginnie Mae), Policy Development and Research, Fair Housing and Equal Opportunity, the Office of Lead Hazard Control and Healthy Homes, the Cybersecurity and Information Technology Fund, and the Office of Inspector General. The bill also provides appropriations to several related agencies, including the Access Board, the Federal Maritime Commission, the National Railroad Passenger Corporation (Amtrak) Office of Inspector General, the National Transportation Safety Board, the Neighborhood Reinvestment Corporation, the Surface Transportation Board, and the U.S. Interagency Council on Homelessness. Additionally, the bill sets forth requirements and restrictions for using funds provided by this and other appropriations Acts.