The Czech–American is considered among one the greatest players of all time, winning a total of 59 Grand Slam titles across singles and doubles.
"This double whammy is serious but still fixable," said in a statement to WTA.
"I'm hoping for a favourable outcome. It's going to stink for a while, but I’ll fight with all I have got."
Czech-born Navratilova, who became a US citizen in 1981, was also diagnosed and beat breast cancer back in 2010.
Navratilova added that the cancer was in Stage 1, and the prognosis are good, with treatments to begin next week.
The cancer was first discovered in early November during the WTA finals when Navratilova noticed a swelling in her neck that did not go down.
"Martina noticed an enlarged lymph node in her neck during the WTA finals in Forth Worth," said Navratilova's representative Mary Greenham. "When it didn't do down, a biopsy was performed, the results came back as Stage 1 throat cancer.
"At the same time as Martina was undergoing the tests for the throat, a suspicious form was found in her breast, which was subsequently diagnosed as cancer, completely unrelated to the throat cancer.
"Both of these cancers are in their early stages with great outcomes."
Greenham said that Navratilova, who now works as a tennis presenter on television and radio, will not travel to Melbourne for the January 16-29 Australian Open but hopes to contribute to the broadcasts remotely.
"Martina won't be covering the Aussie Open for the Tennis Channel from their studio but hopes to join in from time to time by Zoom," said Greenham.
Tennis fans quickly took to social media offering support, including another tennis trailblazer Billie Jean King.
"@Martina is as brave as she is strong," posted King on Twitter. "She has fought this battle before, and she is in our thoughts and prayers."
