Karen Alexa Grasso Montes[4] (born August 9, 1993) is a Mexican professional mixed martial artist who competes in the women's Flyweight division of the Ultimate Fighting Championship (UFC), where she is the former UFC Women's Flyweight Champion.

During the first eighteen months of her career, she amassed an undefeated record of 5 wins (3 by TKO, 2 by decision) and 0 losses.

[15] On August 5, 2017, Grasso faced Randa Markos at UFC Fight Night: Pettis vs. Moreno.

Grasso suffered from a urinary tract infection and was medically advised to stop cutting weight and be placed on antibiotics, as a result she came in at 119 lbs, three pounds over the strawweight limit and was fined 20% of her purse that went to Markos.

[19] Grasso was scheduled to face Angela Hill on August 25, 2018, at UFC Fight Night 135.

[21] Grasso was expected to face Marina Rodriguez on February 2, 2019, at UFC Fight Night 144.

[31] However, on the day of the weigh-ins, Grasso weighed in at 121.5, 5.5 pounds over the non-title strawweight limit of 116 lbs.

[32] In a statement released just hours after the weigh-ins, Grasso apologized for missing weight, and declared she will now be fighting at flyweight.

[33] Grasso was scheduled to face Ji Yeon Kim on June 27, 2020, at UFC on ESPN: Poirier vs.

[38] Grasso was scheduled to face Joanne Wood on November 20, 2021, at UFC Fight Night 198.

[50] Despite being a heavy underdog, she won the bout and earned the title via a face crank in the fourth round.

[53] Grasso made her first title defense in a rematch against Valentina Shevchenko on 16 September 2023, at UFC Fight Night 227.

[55] On February 9, 2024, it was announced that Grasso and Shevchenko would be the coaches for The Ultimate Fighter 32 on ESPN+, which would feature contestants from the middleweight and featherweight divisions.