Tourists fled the scene off the north coast of Sicily and took refuge in the sea as smoke and ash enveloped the island, the BBC reports.
Dozens of people have been evacuated from the village of Ginostra, with the Italian navy reportedly on standby in the event of a wider evacuation.
Some beaches on surrounding Sicilian islands have been closed as a precaution, according to The Guardian.
Local emergency services confirmed a hiker was killed by falling rock, while several others were injured.
Climbing to the 924-metre summit of the volcano is a popular tourist pursuit on Stromboli. The last significant eruption was in 2007.
The Foreign Office updated its travel advice for Italy shortly before 7pm on Wednesday following the eruption.
“There was a volcanic eruption on the island of Stromboli, Sicily, on Wednesday 3 July,” said the FCO. “Local authorities have responded and are monitoring the situation.
“There are no reports of significant impact on populated areas, but local authorities are assisting those on the island who wish to leave. If you are in the area, you should follow the advice of local authorities.”