CK Hutchinson Holding Limited, the parent company of 3 Italia, and VimpelCom, the owner of Wind, said they had reached an agreement for a joint venture which will be operated on an equal basis and be comprised of their activities in Italy.
"Wind and 3 Italia are going to acquire through the integration of their activities the size and the necessary efficiency to continue to offer services at competitive prices," the groups said in a statement.
The combined revenues of the two telecom companies was €6.4 billion in 2014, the statement added.
Besides mobile customers, they will also serve 2.8 billion fixed telephones.
"The union of 3 Italia and Wind is going to create a financially solid and efficient operator, capable of competing at a high level in the market," said Cannig Fok, a senior executive at CK Hutchinson.
The merged firm will have a board of directors with three members from each company, with the chairman changing every 18 months.