Holy Roman Emperor Otto III died unexpectedly from a fever (possibly smallpox) on January 23, 1002 at age 21, from a sudden fever while on campaign near Civita Castellana while attempting to retake Rome from rebellious aristocrats.
His death, before he could be married to the Byzantine princess Zoe, threw the Empire into political crisis due to the lack of a clear heir. Otto III was succeeded by his second cousin Henry II who was crowned King of Germany in 1002 and Holy Roman Emperor in 1014.