The film marked one of the last films to be scored by James Horner, and one of three posthumous releases to feature his music. The film and the film's soundtrack album are dedicated to his memory.
Billy "The Great" Hope is an undefeated professional boxer living in the suburbs of New York City with his wife Maureen and their daughter Leila. During a match in which he defends his light heavyweight world title, Billy sustains an eye injury and is convinced by Maureen to retire while he's on top. After the match at a press conference, an up-and-coming boxer Miguel "Magic" Escobar taunts Billy and tries to get Billy to fight him. At a charity event for the orphanage where he and his wife both grew up, Escobar is in attendance, and as Billy is leaving, Escobar threatens he'll take Maureen and his title away from him, and while Maureen tells Billy to let it go and go home with her, Billy's anger gets the best of him, leading to a brawl in which Maureen is accidentally shot and killed by Miguel's brother Hector, who flees.
Billy begins abusing alcohol and drugs while obsessively searching for Hector. He eventually gets a tip about Hector's whereabouts but only finds Hector's drug-addicted wife Maria, and leaves after learning Hector is a father. After attacking a referee out of frustration after throwing a fight, Billy is suspended and left indebted, leading to his house and belongings being repossessed. He continues to spiral out of control and nearly dies after crashing his car in a suicide attempt, which also causes him to lose custody of Leila, who is put under care of Child Protective Services officer Angela Rivera. The incident drives Billy to sober up, but Leila cuts ties with him, blaming him for their predicament.
At the behest of friends, Billy gets a job as a cleaner at a gym owned by seasoned boxer Titus "Tick" Wills, and eventually convinces Tick to become his trainer. Billy's former manager, Jordan Mains, who is currently managing Miguel, arranges a fight between the two that could put Billy back in the spotlight. Tick is reluctant to train Billy, fearful he might be blinded by his vendetta against Miguel, but is motivated to do so when another of his students, Hoppy, is killed by his abusive father while attempting to defend his mother.
Seeing Billy's hard work after securing a job and keeping it, and his ability to show responsibilities of a father, the judge removes his visitation restrictions and congratulates him for his good work. Billy then takes Leila to his apartment where they have breakfast together and Leila asks if she can attend the fight. Billy, reluctant to let his daughter go to the fight because Maureen never wanted to expose their daughter to the violence in boxing, says he is unsure because Maureen used to make all the decisions for him. Leila asks if they can go visit Maureen's grave, where Leila convinces Billy to let her go to the fight to have someone by his side. Billy tells Leila that there will be people at the fight saying some harsh things, so Leila makes an agreement to go to the fight but stay only in the locker room with Angela, watching the fight via closed circuit television in the locker room.
As the match begins, Miguel has the upper hand against Billy, but, with Tick's advice, Billy has the chance to turn the tables in the final round by using the Philly shell defense and countering more aggressively with his left. As the round reaches its final minute, Billy pivots hard and, although fighting from a traditional stance, delivers a powerful left uppercut which sends the champion down to the ground. Miguel manages to get up before the count is over and is saved by the bell. Billy is declared the winner by a split-decision and reunites with Leila in the locker room, where she forgives his past mistakes and they embrace.
Eminem was originally supposed to play the role of Billy Hope. The film's screenwriter Kurt Sutter said the project was inspired by the rapper's personal struggles. He stated that he had taken meetings with Eminem's producing partners over the past seven years, looking for something to do together. "I know he's very selective and doesn't do a lot. But he shared so much of his personal struggle in this raw and very honest album, one that I connected with on a lot of levels. He is very interested in the boxing genre, and it seemed like an apt metaphor, because his own life has been a brawl. In a way, this is a continuation of the 8 Mile story, but we are doing a metaphorical narrative of the second chapter of his life. He'll play a world champion boxer who really hits a hard bottom, and has to fight to win back his life for his young daughter. At its core, this is a retelling of his struggles over the last five years of his life, using the boxing analogy. I love that the title refers to Marshall being a lefty, which is to boxing what a white rapper is to hip hop; dangerous, unwanted, and completely unorthodox. It's a much harder road for a southpaw than a right handed boxer." Producers Alan and Peter Riche have given a slightly different story about Eminem's involvement however stating that they set out to make a boxing movie similar to The Champ but wanted to make the story about a father-daughter relationship as opposed to The Champ's father-son story. Recalling Eminem's strong relationship with his daughter they then asked him who was immediately receptive.
On December 13, 2010, DreamWorks acquired the script, with Eminem eyed to play the lead role. however the following August the studio dropped the project. Metro-Goldwyn-Mayer picked up the film that October. in December 2012, Eminem dropped out of the film to focus instead on his music. Antoine Fuqua signed on to the project in March 2014 with Jake Gyllenhaal replacing Eminem. Other casting news was announced in May 2014 with Forest Whitaker, Lupita Nyong'o, and Rachel McAdams officially joining the cast. In August of that year, it was announced that Naomie Harris would be replacing Nyong'o.
Gyllenhaal did research for his role by doing "tons of reading on boxers, orphan boxers, the spirit of gyms all over America, children who start early, [and] the history of foster care in America." while also spending five months training as a boxer. Eminem would later praise Gyllenhaal's performance noting that "Jake smashed it" in an interview with Zane Lowe.
Southpaw marks the first investment in an American film by Wanda Pictures, a division of Wang Jianlin's Chinese conglomerate Dalian Wanda Group. Principal photography began on June 16, 2014. Filming took place in Pittsburgh and Indiana, Pennsylvania, and sets in New York City.
The film had its world premiere at the 2015 Shanghai International Film Festival on June 15, 2015, where it was in competition, and was released on July 24, 2015, by The Weinstein Company.
Southpaw grossed $52.4 million in North America and $38.5 million in other territories for a total gross of $92 million, against a budget of $25 million.
In its opening weekend, the film grossed $16.7 million from 2,772 theaters, finishing 5th at the box office.
The review aggregator website Rotten Tomatoes gives the film a rating of 61%, based on 207 reviews, with a rating average of 6/10. The site's critical consensus reads, "Jake Gyllenhaal delivers an impressively committed performance, but Southpaw beats it down with a dispiriting drama that pummels viewers with genre clichés." On Metacritic, the film has a score of 57 out of 100, based on 42 critics, indicating "mixed or average reviews". On CinemaScore, audiences gave the film an average grade of "A" on an A+ to F scale.
Soren Anderson of The Seattle Times gave the film two and a half stars out of four, saying "Southpaw, a boxing movie with a theme of redemption, is redeemed by the performances of its two main actors, Jake Gyllenhaal and Forest Whitaker." Kyle Smith of the New York Post gave the film one and a half stars out of four, saying "It brings back every stale genre convention you can think of, then hopes you won't recognize predictability pumped up with swearing and steroids and an Eminem song during the training montage." Ty Burr of The Boston Globe gave the film two and a half stars out of four, saying "This is a genre with especially sturdy bones, and when Southpaw connects, which is more often than you might expect, you feel it down to your toes." Ann Hornaday of The Washington Post gave the film one and a half stars out of four, saying "Southpaw may be rote, predictable and mawkish, but none of those faults lie in its star. Even when he looks like an unholy mess, he transcends the movie he's in." Steven Rea of The Philadelphia Inquirer gave the film three out of four stars, saying "What keeps this cornball business from getting out of hand is the commitment of Gyllenhaal, whose performance is fierce and muscular, in and out of the ring." Michael Phillips of the Chicago Tribune gave the film two and a half stars out of four, saying "The script may have hamburger for brains, but Fuqua slams it home with the help of actors who give their all - even when giving a little less might have made things more interesting."
Peter Howell of the Toronto Star gave the film two and a half stars out of four, saying "This isn't great cinema, but it's satisfying movie-making, with nothing more on its mind than telling a heart-tugging story." A. O. Scott of The New York Times said, "I wish I could say Southpaw was a knockout, or even a contender, that it went the distance or scored on points. But it's strictly an undercard bout, displaying enough heart and skill to keep the paying customers from getting too restless." Benjamin Nugent of The New York Times has compared the film to Robert De Niro stating, "Pity Jake Gyllenhaal, who despite getting shredded for Southpaw, could not outbox the shadow of Robert De Niro's Raging Bull performance." Chris Nashawaty of Entertainment Weekly gave the film a C+, saying "Just as director Antoine Fuqua starts to close in on something interesting and unexpected, he retreats to the safety of his corner and gives us what we've seen too many times before: a predictable flurry of melodramatic jabs." Barbara VanDenburgh of The Arizona Republic gave the film three out of five stars, saying "Southpaw is all about the fist. There's no delicate footwork here, no lingering grace notes. It's a film played entirely in power chords." James Berardinelli of ReelViews gave the film three out of four stars, saying "Southpaw isn't content with presenting a gallery of clichéd characters. It takes the time to put flesh on the bones." Colin Covert of the Star Tribune gave the film one out of four stars, slamming Gyllenhaal's performance, saying "As a troubled slugger, Gyllenhaal is impressively muscle-bound, but gives no knockout performance. His work drags on like 12 rounds of fistfight fatigue."
Eminem executive-produced the soundtrack, which was released by Shady Records on July 24, 2015. He had previously released his single called "Phenomenal" from the soundtrack on June 2, 2015.
An album of James Horner's score was released through Sony Classical on July 24, 2015. This was Horner's final score (it was recorded after The 33, although Southpaw was released first); he was killed in a plane crash on June 22, 2015.