The guide was attacked on Monday after the group left their vehicle to inspect a pride of lions with cubs under a tree in the Hwange National Park, the country's largest natural reserve.
"Some cubs came near the tourists and one adult lion identified as Nxaha charged at them," police spokeswoman Charity Charamba told AFP.
"The adult lion retreated for a while and then came charging at the guide. It knocked him down and mauled him on the neck and shoulder."
The guide, Quinn Terence Swales, 40, was airlifted from the scene but pronounced dead on arrival at a hospital in the resort town of Victoria Falls.
Owners of the safari camp confirmed the incident in a statement.
"It is with deep regret and great sadness that we are able to confirm the death of Quinn Swales, a Camp Hwange professional guide, who was fatally mauled by a male lion whilst out on a walking safari," Camp Hwange said.
"We can confirm that Quinn did everything he could to successfully protect his guests and ensure their safety, and that no guests were injured."
Quinn was leading six tourists when he was killed.
Charamba urged visitors to game parks to "remain wary even when the animals appear friendly because with an animal you can never predict its next move."
The killing of Cecil the lion in July provoked worldwide outrage when it emerged he was a favourite attraction among visitors to Hwange and was wearing a tracking collar as part of an Oxford University research project.
Cecil was reportedly lured with bait from the safety of the park before being killed by Walter Palmer, an American dentist armed with a bow and arrow who paid $55,000 (50,000 euros) to shoot a lion.
Palmer's guide on the expedition, Zimbabwean Theo Bronkhorst, appeared in court last month and was granted $1,000 bail pending his trial on September 28 on charges of organising an illegal hunt.
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.