Shevchenko defeated Santos via split decision (48-47, 47-48, 49-46) during the UFC 275 co-main event Saturday night in Singapore to retain the women's flyweight title.
"You're never satisfied with your performance. ... But I did everything," Shevchenko said in her postfight interview. "I left my heart in this Octagon."
Santos was nearly a 6-to-1 underdog for her first UFC title opportunity - the narrowest odds in a Shevchenko bout since the latter became champion in 2018. The Brazilian fighter had a strong start in the bout, controlling Shevchenko on the ground and attempting submissions at several points of the first three rounds.
Though Santos racked up control time, she did not do too much damage when Shevchenko was on the ground. During stand-up exchanges at other points of the opening 15 minutes, Shevchenko landed more shots than the challenger as the quicker and sharper striker, making some of the early rounds very close.
However, the momentum swung in Shevchenko's favor in the fourth after a clash of heads led to significant swelling on Santos' eye. The injury visibly seemed to bother her, and the challenger said in her postfight interview she couldn't see out of that eye. Shevchenko got more aggressive and landed sharp combinations on Santos down the stretch before taking her down late in the fifth and riding out the victory.
This marked the first time a judge scored a fight against Shevchenko during her title reign, which began in December 2018.
Santos' manager revealed that she suffered a broken orbital bone and will undergo surgery upon her return to Brazil, according to MMA journalist Ariel Helwani.
With the victory, Shevchenko - the No. 1-ranked women's pound-for-pound fighter in the UFC - has now successfully defended the 125-pound belt seven times. She passed Ronda Rousey for the most title defenses in a single women's division in UFC history and tied Amanda Nunes for the most overall. Only Demetrious Johnson, Jon Jones, Anderson Silva, and Georges St-Pierre have more than seven UFC title defenses.
"Bullet" is now riding a nine-fight winning streak overall and remained undefeated at flyweight. Shevchenko, 34, has not lost since Nunes won a split decision in their 2017 rematch for the women's bantamweight title, after which Shevchenko decided to move down in weight.
Shevchenko has multiple options for her next move. There has been talk about her returning to bantamweight to challenge Julianna Pena or Nunes for a second belt, but she also mentioned Saturday night that she could face Miesha Tate in an eighth defense. That matchup would depend on whether Tate, a former women's bantamweight champion, defeating Lauren Murphy in her 125-pound debut at UFC 276 on July 2.
Santos, 28, will gain the respect of MMA fans after seriously testing Shevchenko as a big underdog, but she ultimately had her four-fight winning streak snapped to fall to 4-2 in the Octagon.