Blue crab may refer to:

• Blue Crab 11, an American sailboat design
• Callinectes sapidus – Chesapeake or Atlantic blue crab of the West Atlantic, introduced elsewhere
• Cardisoma guanhumi – blue land crab of the West Atlantic
• Discoplax celeste – blue land crab of Christmas Island
• Paralithodes platypus – blue king crab of the North Pacific
• Portunus pelagicus – blue swimmer crab of Australia and Southwest Pacific
• Portunus segnis - a Western Indian Ocean species, was recently recorded in Tunisian waters, where it is invasive
• Portunus trituberculatus – Japanese blue crab of the Northwest Pacific