The year 1866 in architecture involved some significant events.

Buildings and structures

Buildings

• The seat of the Norwegian Parliament, Storting building, designed by Emil Victor Langlet, Inaugurated 5 March
• The building of Nationalgalerie starts in Berlin, designed by Friedrich August Stüler and Johann Heinrich Strack.
• The New Synagogue, Berlin, Germany is completed by Friedrich August Stüler to the design of Eduard Knoblauch.
• St. Mark's Church, Royal Tunbridge Wells, England, designed by Robert Lewis Roumieu, is consecrated.
• The Princess Theatre, Melbourne, Australia by architect William Pitt is completed.
• Basilique Notre-Dame de Marienthal is completed

Awards

• RIBA Royal Gold Medal – Matthew Digby Wyatt.
• Grand Prix de Rome, architecture: Jean-Louis Pascal.

Births

• February 15 – Banister Fletcher, English architect and architectural historian (died 1953)
• February 23 – Joseph Miller Huston, American architect working in Pennsylvania (died 1940)
• June 14 – Henry Sproatt, Canadian architect (died 1934)
• July 14 – Ragnar Östberg, Swedish architect (died 1945)
• July 29 – Jens Zetlitz Monrad Kielland, Norwegian architect (died 1926)
• August 1 – Claude Fayette Bragdon, American architect (died 1946)
• November 28 – Henry Bacon, American Beaux-Arts architect (died 1924)

Deaths

• March 23 – Ferdinand von Arnim, German architect and watercolor painter (born 1814)