The men were gorilla trekking at Virunga National Park on the eastern border when their convoy was ambushed by armed militants.
Britain's Foreign Secretary Boris Johnson on Sunday announced that the two Britons held hostage in the Democratic Republic of Congo have been released unharmed.
It was the deadliest attack in recent years and took the total number of rangers killed in the park to 175.
He added: "My thoughts are now with the family of Virunga Park ranger Rachel Makissa Baraka who was killed during the kidnapping, and with the injured driver".
Park director Emmanuel de Merode said: "Ranger Baraka's life was tragically cut short in service to Virunga National Park".
Security guard Katumwa, 25, was killed defending the British pair, becoming the first female ranger in the history of the park to be murdered by bandits.
"We want to convey our deepest condolences to her family and our honest gratitude for her courage in the service of Congo".
The Foreign Office had been in contact with local authorities since the event took place.
Cosma Wilungula, head of the Congolais Institute for the Conservation of Nature (ICCN), praised the work of the "brave team" that resulted in a "quick resolution of this incident".
The BBC's Louise Dewast, reporting from the country's capital Kinshasa, said there were armed groups operating in the park and there had been kidnappings before, with half involving a ransom demand.
Congolese soldiers and park rangers have launched an operation to locate two British tourists kidnapped in the country's volatile eastern borderlands, an army spokesman said.
The park, which is a Unesco world heritage site, is home to critically-endangered mountain gorillas, lions, elephants and hippos.
Last year, a fifth of the park's southern sector was deforested owing to illegal charcoal production.
The Foreign Office now - and before the kidnapping - advises against travelling to the area.
It said that United Kingdom government staff were not always in the area and the British embassy's ability to offer consular assistance could be "severely limited".