Known as "The General," Mered Medhanie, 35, was one of the world's most-wanted people smugglers and suspected of being central to the mass movement of migrants between the continents.
He arrived Tuesday night in Rome and is expected to appear before a judge Wednesday, Britain's National Crime Agency said.
Countries form the European Union have struggled to prevent thousands of deaths in the Mediterranean Sea as migrants arrive on their shores in overcrowded, unsafe vessels from the North African and Turkish coasts.
European law enforcement officers are focusing on bringing to court people smugglers who take money from migrants to organize the perilous journeys.
The National Crime Agency said it had tracked Medhanie's address in Khartoum, Sudan, and worked with Sudanese police to have him arrested.
Citing Italian prosecutors, the agency said he is believed to be responsible for the October 2013 shipwreck off the Lampedusa coast
in which more than 300 asylum seekers, mostly from Eritrea, drowned in sight of the Italian island. It described him as a "mastermind" of a major smuggling operation.
"Medhanie is a prolific people smuggler and has absolute disregard for human life," Tom Dowdall, deputy director of the National Crime Agency, said in a statement.
"Medhanie no doubt thought he was beyond the reach of European justice but we were able to support the Italians by tracking him down to Sudan," he said.
Medhanie has been dubbed "The General" because he apparently styles himself on the slain former Libyan dictator Moammar Gadhafi
, according to Italian prosecutors.
The National Crime Agency said that Italian authorities had intercepted Medhanie's telephone conversations to confirm he was behind regular trips on the Mediterranean to Europe and was coordinating other smugglers.
In one conversation, Medhanie "was heard laughing about the fatal overloading of migrant ships," the agency said.
More than 2,500 migrants have died
trying to cross the Mediterranean this year.