Rescuers have drilled through to the underground chamber where 33 Chilean miners have been trapped since August.
The breakthrough at the San Jose mine came shortly after 0800 local time (1200 GMT), sparking celebrations.
It means efforts to remove the miners through the tunnel should begin within days.
The men were trapped when part of the mine collapsed on 5 August - their 65-day ordeal is the longest suffered by a group of miners caught underground.
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Chile's Trapped Miners
Twitter: Tim Willcox at the scene
Graphics: Guide to rescue
Mine rescue timeline
They have been living in a shelter 700m (2,300ft) underground. However, the Plan B drill - the second of three which have been working simultaneously - has penetrated 624m to a workshop which can be reached by the miners.
Officials say they still need to determine whether the miners can be winched up through the exposed rock, or if they will have to wait for the shaft to be encased with steel piping.
Huge cranes have been brought in to lower the metal casing if it is needed.
Chile's Mining Minister Laurence Golborne has warned that it will be three to eight days before the rescue mission can begin.
Officials say everything needed for the rescue is now in place.
Relatives of the miners, many of whom have been camping near the mine since the collapse, milled around in excitement at the news. Sirens wailed in celebration.
Alicia Campos, the mother of trapped miner Daniel Herrera, said she was "very happy".
"I have a huge sense of relief because I feel I'll see my son soon," she told the BBC.
It has been a long wait for the families, says the BBC's Tim Willcox at the scene.
For weeks they have been anxiously awaiting any snippet of news, and grabbing short opportunities to speak to their loved ones by phone.
Many families waited up all night in expectation of the breakthrough, our correspondent says.
When the rescue operation begins, a medic will be sent down the shaft initially, in a special capsule, to assess the miners. Then it is expected to take an hour to winch each man to safety.
The men are expected to be split into three groups. Some who are fit and have the most technical know-how will be chosen to go first - in case something goes wrong.
Then the weakest are expected to be brought to the surface.
A final group, including some of the strongest miners, will wait till last.