The turtles, from the Chelonia mydas species that is protected in Indonesia, were released on Kuta beach after they were rescued during a Navy operation against poachers in December.
Tourists gathered to watch and film the release on their mobile phones, cheering the turtles on as they trudged across on the beach.
"This is a rare animal that must be preserved," said Merry Christian, a 46-year-old local tourist.
Indonesia has become a hub of international trafficking of marine turtles, feeding demand from countries like Malaysia, Vietnam and China. Anyone convicted of involvement in the trade can be jailed for up to five years under Indonesian law.
The turtles had been in rehabilitation at the Bali Conservation and Natural Resources Agency, authorities said.