Carolus, the Latin form of Carl, may refer to:

• Carolus Linnaeus (Carl von Linné), Swedish botanist and physician
• Carolus Linnaeus the Younger (Carl von Linné or Linnaeus filius), Swedish naturalist
• Carolus-Duran (Charles Auguste Émile Durand), French painter
• Carolus Sigonius (Carlo Sigonio or Sigone), Italian humanist
• Carolus Magnus (Charlemagne), Holy Roman Emperor
• Carolus Clusius (Charles de l'Écluse), Flemish doctor and botanist
• Carolus Rex (Charles XII or Karl XII), King of Sweden
• Carolus Gustavus (Charles X Gustav or Karl X Gustav), King of Sweden

Carolus may also refer to:

• carolus (coin), was a gold coin struck in the reign of Charles I.
• Carolus (genus), a genus of six species in a family of flowering plants.
• 16951 Carolus Quartus, an asteroid named after Charles IV (Carolus Quartus), the Holy Roman Emperor and King of Bohemia.
• Several Swedish ships of the line have also been named Carolus.