John was King of Saxony from 9 August 1854 until his death in 1873. He was a member of the House of Wettin. During his reign, Saxony became a part of the German Empire.

The House of Wettin was a dynasty of German kings, prince-electors, dukes, and counts that once ruled territories in the present-day German states of Saxony, Saxony-Anhalt and Thuringia. The dynasty is one of the oldest in Europe, and its origins can be traced back to the town of Wettin, Saxony-Anhalt. The Wettins gradually rose to power within the Holy Roman Empire. Members of the family became the rulers of several medieval states, starting with the Saxon Eastern March in 1030. Other states they gained were Meissen in 1089, Thuringia in 1263, and Saxony in 1423. These areas cover large parts of Central Germany as a cultural area of Germany.