1666 in Denmark

Incumbents

• Monarch – Frederick III

Events

• 11 February; Denmark-Norway agrees an offensive alliance with the Dutch Republic against England, and enters the Second Anglo-Dutch War;
• 1 August – Anders Bording's Den Danske Mercurius, Denmark's first newspaper, is published for the first time.

Undated

• Holmen Cemetery, the oldest cemetery in Denmark still in use, relocates to its current location in Østerbro

Births

• 22 February – Christian Christophersen Sehested, nobleman
• 16 June – Johan Conrad Ernst, architect

Deaths

• 23 September Hannibal Sehested, diplomat
• 30 October – Iver Krabbe, nobleman and military officer