Canada’s Barrick Gold is buying Randgold Resources, creating the world’s biggest gold miner with a value of about $18bn (£14bn).
The firms own some of the world’s most valuable gold fields, producing more than 6.6 million ounces of gold a year.
Barrick shareholders will end up own two-thirds of the combined firm and Randgold will own the remaining third.
Shares of both firms have fallen almost 30% this year, amid falling gold prices and questions over their strategy.
“Our industry has been criticised for its short-term focus, undisciplined growth and poor returns on invested capital. The merged company will be very different,” said Mark Bristow, Chief Executive of Randgold.
“Its goal will be to deliver sector leading returns, and in order to achieve this, we will need to take a very critical view of our asset base and how we run our business, and be prepared to make tough decisions,” he added.