The 6.0-magnitude quake struck in the middle of the night near the city of Bologna.
Two people were killed in Sant'Agostino when a ceramics factory collapsed. Another person was killed in Ponte Rodoni do Bondeno, emergency workers were quoted as saying by Italy's Ansa news agency.
About 50 people were injured -- but none seriously, reports say.
Aftershocks have been reported, with the earthquake felt in Bologna, Ferrara, Verona, and Mantua.
Rescue teams were combing the area amid reports that people may be buried under rubble.
In January, a 5.3-magnitude quake hit northern Italy but caused no injuries.
The last major tremor to hit the country killed nearly 300 people in the central town of L'Aquila in 2009.