UFC superstar Amanda Nunes has tested positive for COVID-19 … and her fight against Julianna Pena next weekend at UFC 265 is off.

The UFC is planning to reschedule the title fight once Amanda is 100% healthy.

Nunes and Pena were scheduled to be the co-main event of the August 7 event … on a card that also features a highly anticipated heavyweight matchup pitting Derrick Lewis and Ciryl Gane against each other.

The events going down at the Toyota Center in Houston, TX.

It’s a matchup 31-year-old Pena — who has wins over Cat Zingano and Jessica Eye — has been champing at the bit for … previously telling us she was the GOAT’s “kryptonite.”

Interesting to note, back in June 2020, Amanda — who’s currently on a 12-fight win streak — speculated she may have battled COVID … saying she experienced all of the traditional symptoms, and was in bed for several days.

Nunes says her wife, UFC contender Nina Nunes, was so sick they took her to the hospital.

No word yet on whether the UFC will replace Nunes-Pena with another fight.

Story developing …