The landmark treaty will establish a legal framework to extend swathes of environmental protections to international waters, which make up more than 60 percent of the world's oceans.
The pact is seen as essential to conserving 30 percent of the world's land and ocean by 2030, as agreed by world governments in a historic accord signed in Montreal in December.
Ocean ecosystems create half the oxygen humans breathe and limit global warming by absorbing much of the carbon dioxide emitted by human activities.
But only about one percent of the high seas are currently protected.
"What happens on the high seas will no longer be 'out of sight, out of mind'," said Jessica Battle, Senior Global Ocean Governance and Policy Expert, who led NGO World Wildlife Federation's team at the negotiations.
"The High Seas Treaty will allow for the kind of oversight and integration we need if we want the ocean to keep providing the social, economic and environmental benefits humanity currently enjoys."