The Britons were among three people abducted by unidentified armed men while visiting Virunga National Park, a renowned gorilla sanctuary in the east of the country.
Foreign Secretary Boris Johnson said he was “delighted to announce” their release.
“I pay tribute to the DRC authorities and the Congolese Institute for Nature Conservation for their tireless help during this terrible case,” he said.
A 25-year-old park ranger travelling with them was killed and their driver was also taken captive, a park spokesman said.
Mr Johnson added: “My thoughts are now with the family of Virunga Park ranger Rachel Masika Baraka who was killed during the kidnapping, and with the injured driver and the released British nationals as they recover from this traumatic incident.”
Their vehicle was ambushed north of the city of Goma, the capital of North Kivu province, on Friday.
The park released a statement saying Ms Baraka was trying to protect two passengers and the driver of the vehicle when it was attacked by armed assailants.
They said she was taken to hospital for treatment but died from her injuries.
The park’s director, Emmanuel de Merode, said: “Ranger Baraka’s life was tragically cut short in service to Virunga National Park.
“She was one of the Park’s 26 female rangers and was highly committed, showing true bravery in her work.
“We wish to extend our sincerest condolences to her family, and our thoughts are with all those affected by this incident.”
The park has experienced an increase in violence in recent months with armed groups staging a series of raids to steal resources, particularly charcoal.
Last month, five young rangers and a driver in the park were killed in an ambush.
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It was the deadliest attack in recent years and took the total number of rangers killed in the park to 175.
Virunga is a UNESCO world heritage site covering 3,000 square miles on the country’s border with Uganda and Rwanda.