T'Challa, played by Chadwick Boseman, the king of Wakanda, is facing the end of his life due to an undisclosed terminal illness. His sister, Shuri, the innovative princess responsible for developing cutting-edge technology for their nation, believes that the heart-shaped herb could provide a cure. However, after it was destroyed by Erik Killmonger, she attempts a synthetic recreation but is unable to succeed before T'Challa passes away.
Fast forward a year, and Wakanda finds itself under immense pressure from various nations seeking to exploit its Vibranium resources, leading some to resort to theft. In her grief over T'Challa’s death, Queen Ramonda urges Shuri to keep working on the herb to help create a new Black Panther to safeguard their land, but Shuri is reluctant, seeing the Black Panther as a relic of the past.
Meanwhile, in the Atlantic Ocean, a CIA and U.S. Navy SEALs operation, equipped with a Vibranium detector, tragically ends when they are ambushed and wiped out by a faction of blue-skinned, aquatic superhumans commanded by Namor, the king of Talokan. This attack arises from Namor's determination to protect his hidden underwater realm, which is now compromised since T'Challa publicly revealed Wakanda's existence.
Namor confronts Ramonda and Shuri, effortlessly overriding Wakanda’s sophisticated defenses. He places an ultimatum before them: deliver the scientist responsible for the Vibranium detector—identified as MIT student Riri Williams—or face the wrath of his formidable forces.
Shuri, alongside Okoye, the formidable leader of the Dora Milaje, learns from CIA agent Everett Ross about Riri’s identity. They attempt to persuade Riri while firmly asserting that Wakanda had no part in the earlier attack. However, their mission turns perilous when they are pursued by both the FBI and Namor’s warriors. Okoye is defeated in the chaos, leading to Ramonda stripping her of her title for not adequately protecting Shuri and siding with Killmonger previously. In search of reinforcements, Ramonda finds Nakia, a former undercover agent for Wakanda, now living in Haiti.
As tensions escalate, Namor shows Shuri the treasures of his underwater kingdom, revealing a tragic history of how his lineage was transformed into powerful beings due to a mystical blue plant from a long-lost era. Determined to forge an alliance against the surface world, he issues a stark warning: refuse him, and the consequences will be dire.
After a daring escape facilitated by Nakia, which costs the life of one of Namor’s guards, tragedy strikes again when Ramonda sacrifices herself in an attempt to save Riri from drowning. Enraged, Namor asserts his promise to return with an immense army, prompting Shuri and her people to retreat for safety to the Jabari mountains.
In the midst of this turmoil, Ross finds himself incarcerated by his ex-wife, CIA director Valentina Allegra De Fontaine, for treasonous actions. Following Ramonda’s funeral, Shuri uses remnants of the plant that grants Namor's people their extraordinary powers to recreate the heart-shaped herb. This risky move gives her superhuman capabilities, albeit at the price of her own health, and leads her to a confrontation with Killmonger in the Ancestral Plane, where he implores her to seek vengeance.
Embracing her new identity, Shuri dons the Black Panther suit, earning the acknowledgment of the various Wakandan tribes. Despite M'Baku encouraging a peaceful resolution, Shuri is resolute in her desire for revenge against Namor, prompting a fierce retaliation against Talokan.
As the Wakandans prepare for battle, led by Ayo, who takes charge of the Dora Milaje, Riri engineers an Iron Man-esque armored suit to join the fight. The Wakandans successfully lure Namor and his forces to the surface where intense combat unfolds. In a climactic duel, Shuri momentarily overpowers Namor but has a vision of her mother, leading her to offer peace rather than vengeance.
In the aftermath of the conflict, Namor accepts the opportunity for alliance, remarking that this new partnership might one day aid in conquering the surface world. Riri returns to MIT, while Okoye makes her move to rescue Ross from captivity. Shuri commits to planting more heart-shaped herbs to ensure the legacy of the Black Panther is preserved.
In a surprising twist, M'Baku emerges as a challenger for the throne during Shuri's absence. Eventually, Shuri visits Nakia in Haiti, performing a ritual that allows her to finally grieve T'Challa.
In a poignant mid-credits scene, Shuri uncovers that Nakia and T'Challa had a son in secret named Toussaint, who reveals that he carries his father’s name, T'Challa, preserving the legacy of the Black Panther for generations to come.
