Which sport is the central topic of the sports drama film "Million Dollar Baby" directed by Clint Eastwood?

"Million Dollar Baby" is a 2004 American sports drama film directed, co-produced, scored by and starring Clint Eastwood from a screenplay written by Paul Haggis, based on short stories by F.X. Toole, the pen name of fight manager and cutman Jerry Boyd. The film follows Margaret "Maggie" Fitzgerald (Hilary Swank), an underdog amateur boxer who is helped by an underappreciated boxing trainer (Clint Eastwood) to achieve her dream of becoming a professional.

"Million Dollar Baby" was theatrically released on December 15, 2004, by Warner Bros. Pictures. It received critical acclaim and grossed $216.8 million domestically. The film garnered seven nominations at the 77th Academy Awards and won four: Best Picture, Best Director, Best Actress (for Hilary Swank), and Best Supporting Actor (for Morgan Freeman).

In the film Margaret "Maggie" Fitzgerald, a waitress from the Ozarks, shows up at the Hit Pit, a rundown Los Angeles gym owned and operated by Frankie Dunn. Dunn is a cantankerous Irish-American trainer, revealed to be estranged from his daughter. Maggie asks Frankie to train her, but he refuses as he doesn't train women and she's "too old" to begin a boxing career. Later he reluctantly agrees to train Maggie. Maggie's career skyrockets, but an accident in the ring leads her to ask Frankie for one last favor.