What happened
Otto I was crowned emperor in Rome by Pope John XII, joining German kingship to an imperial title that later historians conventionally treat as the start of the Holy Roman Empire proper.
Why it matters
This event is the standard boundary marker for the empire's beginning in many historical reference works. It links the East Frankish or German royal tradition to the imperial structure that shaped central Europe for centuries.
Notes
The choice of 962 as a starting point is conventional rather than absolute; some historical narratives instead emphasize Charlemagne's coronation in 800, and there was a gap after Berengar I rather than an uninterrupted western imperial succession.