Martina Navratilova -- one of the greatest tennis players of all time -- just announced she has been diagnosed with Stage 1 throat and breast cancer ... but fortunately, she says her condition is "fixable."
The 66-year-old -- who won 59 Grand Slam titles during her career -- says she learned of her status after discovering an enlarged lymph node in her neck back in November.
"The cancer type is HPV and this particular type responds really well to treatment," Martina's rep said in a statement.
After undergoing tests, a mass was also found in her breast ... which was unrelated to the throat cancer.
Luckily, the rep says both cancers are in the early stages and the outcome is positive.
"This double whammy is serious but still fixable," Navratilova said. "I'm hoping for a favorable outcome. It’s going to stink for a while but I’ll fight with all I have got."
The 9-time Wimbledon winner previously battled breast cancer in 2010 ... and after radiation treatment, she was cleared of the disease six months later.
Navratilova will begin treatment this month ... and will sit out of her usual TV analyst gig for the Tennis Channel at the Australian Open.