"Fighter" received mostly positive reviews from music critics, who praised Aguilera's vocals and the song's empowering lyrics.

The single peaked at number 20 on the US Billboard Hot 100 and was certified double platinum by the Recording Industry Association of America (RIAA).

Elsewhere, the song reached the top ten of several national music charts, including those in the United Kingdom, Canada, Australia, and the Netherlands.

In the book Chicken Soup for the Soul: The Story Behind the Song, Aguilera revealed the occasion, theme and meaning of "Fighter".

[1] The writing process of "Fighter" began during her promotion for her debut album in 1999,[1] when she was "a part of the big craze pop phenomenon".

[4] Meanwhile, a reviewer of Billboard described the song as arena rock-influenced,[5] and AOL Music's Nana-Adwoa Ofori noted the elements of rock and roll.

[9] Brian Hiatt from Entertainment Weekly and Chuck Taylor for Billboard likened the track's musical style to that of Janet Jackson's "Black Cat".

[9] Aguilera speaks the lyrics, "After all you put me through, you'd think I'd despise you / But in the end, I wanna thank you, 'cause you made me that much stronger" on the guitar theme by Dave Navarro.

David Brownie from Entertainment Weekly called it "spunkier than one would expect from a dance-floor strumpet who loves to flaunt her lung power.

"[16] Chuck Taylor writing for Billboard complimented "Fighter" for demonstrating that Aguilera "[has] got the goods to rise above what so many lesser acts depend on for celebrity.

"[11] On behalf of the same publication, Andrew Unterberger wrote that "Fighter" and "Can't Hold Us Down" are two tracks that helped "expand audience expectations of her image and sound.

"[18] The New York Times editor Kelefa Sanneh positively viewed the track's theme as "fearless" and "full of mildly rebellious rhetoric.

"[24] Orlaith Condon of Ticketmaster ranked "Fighter" at number one on the list of Aguilera's best songs ever, calling it "gritty", "emotive" and "the ultimate feminist power anthem".

[25] In the United States, "Fighter" debuted at number 61 on the Billboard Hot 100 chart on April 12, 2003, becoming the week's best-debuting single.

[35] On October 14, 2022, "Fighter" was certified double platinum by the Recording Industry Association of America (RIAA) for shipping more than 2,000,000 copies in the country.

[51][52] Due to its chart success in Australia, the Australian Recording Industry Association (ARIA) certified "Fighter" gold for its shipments of 35,000 copies there.

[53] The music video for "Fighter" was directed by Floria Sigismondi, who revealed that it would display Aguilera "like I don't think she's been portrayed before".

[55] It garnered Aguilera and Sigismondi a Juno Award for Video of the Year at the 2004 ceremony, which was held at Rexall Place in Edmonton, Alberta, Canada.

[65] On June 1, 2007, during the promotion of Back to Basics, Aguilera performed "Fighter" along with "Ain't No Other Man", "Hurt" and "Candyman" at the 2007 Muz-TV Awards.

[71] On June 11, 2010, Aguilera performed "Fighter", "You Lost Me", "Not Myself Tonight" along with a medley of "Genie in a Bottle" and "What a Girl Wants" on The Early Show.

[3] Before performing the song, Aguilera revealed to the crowd, "When I was younger there were a lot of people, as I mentioned before, that were sort of around me for the wrong reasons.

[73] On April 16, 2012, Aguilera performed "Fighter" again on the second season of US reality show The Voice, on which she is one of the judges and coaches, with her "Team Xtina" and Crenshaw High School choir.

[75] In July 2021, Aguilera performed the song for two nights at the Hollywood Bowl with Gustavo Dudamel and the Los Angeles Philharmonic.

[81] The clip also featured several NBA famous acts, including Michael Jordan, Kobe Bryant, Shaquille O'Neal, and Yao Ming.

[82] American actor Darren Criss, portrayed as his fictional character Blaine Anderson, performed the song on the episode "Big Brother" of the FOX popular TV show Glee, aired on April 10, 2012.

[87] In a 2018 interview, American recording artist Lauren Jauregui stated that she was inspired by the song, saying: "Christina is a huge part of my developmental years, just getting into owning who I am (...).

[92] Aguilera also performed "Fighter" in the 2018 comedy film Life of the Party, opposite Melissa McCarthy, where she portrayed herself.