The company said on Friday one of its employees had succumbed to his injuries after "a mine-related accident" at its Bambanani mine in Welkom, in South Africa's Free State province.
An investigation into the incident was underway, Harmony said.
CEO Peter Steenkamp extended his and the company's deepest condolences to family, colleagues and friends "in what is already a very difficult time for all South Africans during the COVID-19 pandemic".
"We continue to reinforce safety across all our operations, and urge all our employees to practice safe behaviour on and off duty," he said.
Harmony had reported a fatality at Moab Khotsong last month and at Kusasalethu and Tshepong earlier this year.
Harmony had reported 10 mineworker fatalities in 2019, including a "mining-related accident" at Bambanani in May, and an 11th fatality in December when a security contractor was fatally wounded in an armed attack on the plant at its Kalgold operation in the North West province.
The Bambanani operation, where mining is at a depth of about 2,219m, is in the final stages of its life.
It had been expected to produce 77,000 ounces of gold in FY20 but Harmony withdrew guidance in May, due to the impact of COVID-19 and continued uncertainty regarding when its South Africa mines would be allowed to return to full production following the country's lockdown in March.
Harmony (JSE: HAR) shares hit a one-year high of ZAR11,727c on Friday as the gold price surged past US$1,900/oz for the first time since 2011.
They closed at 11,650c, capitalising the miner at R69.5 billion (US$4.2 billion).
