After refusing for months to give "a running commentary" on Britain's negotiating strategy, May offered the clearest indication to date of the country's departure plans, which were set in motion by last June's referendum on Britain's EU ties.
May said Britain wants to be "the best friend and neighbour to our European partners" but cannot be "half-in, half-out" of the bloc, which was born from the ashes of World War II and is designed to prevent future conflict by uniting Europe around a common economic and political project.
"We do not seek to hold on to bits of membership as we leave," she said.
She went on to reject preexisting models for quasi-membership that have been favoured by those seeking "a soft Brexit". Her remarks instead point to a jarring departure that transforms Britain's relations with Europe.
Britain, she said, will jettison membership in both the single market - which guarantees the free flow of goods, services and people across national boundaries - as well as the customs union, which dictates the terms of trade between Europe and the outside world.
Instead, she said, Britain will seek preferential trade access to European markets through a new agreement. And she said the country would strike out on its own in negotiating trade deals outside the EU.
Such a break has been widely anticipated, though never formally spelled out.