Answer
Rose Namajunas defeated Joanna Jędrzejczyk by first-round knockout to win the UFC Strawweight title in 2017. Namajunas' victory was considered a major upset, as Jędrzejczyk was the reigning champion and had been undefeated in her previous 14 fights. Namajunas' win made her the first American woman to win a UFC title in the strawweight division.