The European Commission on Sunday hailed a first international treaty to protect the high seas agreed by UN member states as a "historic moment".
The full wording of the text was not immediately released but activists hailed it as a breakthrough moment for the protection of biodiversity after more than 15 years of discussions.
"A historic moment for our Ocean... We take a crucial step forward to preserve the marine life and biodiversity that are essential for us and the generations to come," said EU environment commissioner Virginijus Sinkevicius.
"Today marks the culmination of more than a decade of preparatory work and international negotiations in which the EU played a key role," he added, saying he was "very proud of our outcome".
The high seas are a fragile and vital treasure that covers nearly half the planet, and the treaty is seen as essential to conserving 30 percent of the world's land and ocean by 2030.
That objective was agreed by world governments in a historic accord signed in Montreal in December.