The Merchant Mariner Credential (MMC) is a credential issued by the United States Coast Guard in accordance with guidelines of the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW) to United States seafarers in order to show evidence of a mariner's qualifications.[1] It is the standard documentation required for all crew members of U.S. ships for all vessels required to operate with a licensed Master or Operator, regardless of size. The MMC replaced the Merchant Mariner's Document, merchant mariner license, Certificate of Registry, and STCW Certificate.