Stop Fentanyl Money Laundering Act of 2023 This bill expands efforts to prevent money laundering related to international fentanyl and narcotics distribution. The bill allows the Department of the Treasury to impose restrictions on an entity or activity determined to be of primary money-laundering concern in connection with illicit fentanyl and narcotics trafficking. Specifically, if Treasury determines that a foreign financial institution, class of transaction, or type of account is of such concern, Treasury may require domestic financial institutions and agencies to take special measures, such as reporting certain financial transactions involving that entity or activity. The Financial Crimes Enforcement Network (FinCEN) must issue advisories to financial institutions about how to identify Chinese money laundering that facilitates the trafficking of fentanyl and other synthetic opioids. FinCEN must also issue guidance to financial institutions for filing suspicious transaction reports related to suspected narcotics trafficking by transnational criminal organizations. The Government Accountability Office must report on the implications of the Department of State designating Mexican drug cartels as foreign terrorist organizations.