Crowds in St Peter’s Square cheered and bells rang out as the smoke appeared.
The name of the new Pope is expected to be announced shortly.
He will replace Pope Benedict XVI, who stepped down last month saying he was no longer strong enough to lead the Church.
The 115 cardinals have been in isolation since Tuesday afternoon, and held four inconclusive votes before electing a Pope.
Before the conclave began, there was no clear frontrunner to replace Benedict.