Historical Events in 866 AD
- Nov 13 Pope Nicholas I answers the envoys of Boris (Ad consulta vestra)
Famous People Born in 866 AD
- Sep 19 Leo VI Sophos, Byzantine Emperor (886-912) and writer (Problematica), born in Constantinople (d. 912)
Famous People Who Died in 866 AD
- Jan 10 Lin-chi I-hsuan [J Rinzai Gigen], Zen teacher, dies
- May 27 Ordono I, King of Asturia (850-66), dies
- Sep 15 Robert the Strong, Margrave of Neustria