Serena Williams Says Her Breast Milk Helped Heal Her Facial Sunburns -

MILK-TOK

Serena Williams has G.O.A.T. DNA on the court and apparently in her breast milk too ... 'cause the tennis legend says just a couple drops of her boob juice healed her painful sunburns!!

The 42-year-old -- who gave birth to her second daughter in August -- shared the unique remedy with her 1.6 million followers on TikTok ... just after she said an outing in the sun left her under-eye areas in a heap of pain.

Williams explained in a 46-second video that she had been told that putting breast milk on her kids' wounds could help speed up their healing processes ... so she said she figured she'd "try it for like a week" and "see how it goes."

Gallery Launch Gallery Serena Williams Family Photos Launch Gallery

"It works for my kid," she said in the video, before dabbing it on her face.

And, as it turns out -- a few days later, she was pain-free!!

"Ok is this totally weird???" Williams said in a caption on the vid. "I have to say after a week of using MY breast milk under my eye - it worked!"

MERRY ELFIN' CHRISTMAS!!!

In even better news for Williams -- she said in her clip she "has a lot of extra" breast milk ready to go ... so it seems any future fights with the sun will be covered from here.

Yeah ... move over, Aloe Vera!!!