The Fold will go on sale in just over two months time, earlier than many expected, BBC reported.
The Galaxy S10 5G features the firm's biggest-ever non-folding phone display and promises faster data speeds when %G network connectivity becomes available.
The S10 line-up also includes the introduction of a lower-cost model.
Samsung had previously acknowledged that the cost of its S9 range had contributed to "lower-than-expected sales".
Samsung said the Galaxy Fold would open up to create a 7.3in (18.5cm) tablet-like display and would be able to run up to three apps at once.
A demo showed off "app continuity" features by which the device transferred from one mode to another much more smoothly than had been the case with an earlier foldable phone - Royole's FlexPai.
One example involved a Google Maps screen appearing on the Fold's smaller front display and then expanding to a larger view when the handset was opened following a one-second pause.
Samsung added that Whatsapp, Facebook, YouTube and Microsoft Office would also be optimized to suit the new form-factor.
It said that it had designed a new type of hidden hinge system that would withstand hundreds of thousands of folds and unfolds, and contained a battery on each side to extend its runtime.
In addition, the South Korean firm said the phone contained six cameras - three on the back, two on the inside and one on the front - to ensure it could take photos however it is held.
A 4G version of the Galaxy Fold is set to go on sale on April 26 and will start at $1,980. A more expensive 5G edition was also promised.