In 1944, with the help of wealthy Greek weapons manufacturer Ares Buchanan, the human form of the Greek god of war, the Nazis build a large generator designed to harness interdimensional energy that will aid them in defeating the Allies. Buchanan opens the portal with the aid of his disciples, Baroness Paula von Gunther and the mysterious masked femme fatale Doctor Poison, expert of all toxins and Adolf Hitler's top assassin. An Allied air strike team is sent to destroy the portal, guided by a young David Trevor. The German team is killed and the generator is destroyed, seemingly killing Ares in the process, while Haupstein and Kroenen escape. Trevor's jet is shot down by one of the last German soldiers and he crash lands on a mysterious island in the middle of the Pacific Ocean, Themyscira. Trevor is found by Diana, daughter of the island's Queen Hippolyta. Trevor learns that Themyscira is inhabited by an ancient race of immortal warrior women known as Amazons. Diana, who has grown angry with her mother in recent times, jumps at the chance to bring Trevor back to the Americas. Finally achieving freedom from Hippolyta, Diana decides to stay in America, taking up the name Diana Prince and residing in New York.
In modern day, agent of the US government Steve Trevor visits his grandfather David Trevor on his death bed. David tells Steve of his encounter with the Amazons, and Diana, who he has not seen in years. Steve at first believes David's ramblings to be the fantasies of a crazy old man, but then decides to track down Diana Prince. He contacts her online, and the two meet in Central Park. Steve talks to Diana about his grandfather's story, including how Ares Buchanan and the Nazis attempted to harness interdimensional energy. Diana tells Steve to leave, and so he does, only to be attacked by a group of muggers. With his army training he is able to defeat most of them, but one of them shoots at him. Diana appears and blocks the bullet with her indestructible wrist band. Steve is amazed, and Diana takes him with her to her apartment. Meanwhile, Doctor Poison and Paula von Gunther, neither of which having aged since World War II, resurrect Ares in the mountains of Moldova using an evil ritual and the three awaken an ancient Greek monster known as the Hydra. After Steve heads home, Ares appears in Diana's apartment and watches over her as she sleeps. She awakens and attacks him. The two engage in a brief but fierce battle, almost destroying the entire apartment complex. Ares flees, and Diana goes to Steve, warning him about the coming of Ares. Steve, being a government agent, goes to General Wade Eiling with this information, but Eiling dismisses his warnings as nonsense. Meanwhile, Diana dons her Amazon battle armor and weapons, only to be attacked by the Hydra.
During their battle through the streets of Manhattan, Diana notices that the Hydra is laying eggs. She kills the Hydra, but realize it's offspring could hatch at any minute. Concluding the eggs are in the sewer, Diana goes down into the sewer to destroy them. Diana is injured while looking for the eggs, and attacked by Doctor Poison. Diana manages to tear off Doctor Poison's mask and expose her to her own toxic gas, defeating her. Diana destroys the last of the Hydra's eggs and meets up with Steve, bringing the unconscious Doctor Poison to the bureau. Eiling is impressed by Diana and tries to recruit her as a government agent. Diana refuses, and the next day Steve takes her out for coffee and to talk. At the government base, Ares appears at the bureau, confronting General Eiling. Ares offers him a vision of the future, showing that he and his servants will destroy the world. Ares stabs Eiling and leaves him for dead, stealing the blueprints for the Nazi machine from the government archives and disappearing with Doctor Poison.
Steve and Diana return to the base just in time to save Eiling. Steve, using a GPS tracker that was secretly placed on Doctor Poison, locates her and Ares at the Oracle of Delphi in Greece. Steve flies Diana to Greece, but their jet is shot down by Paula von Gunther. Diana saves Steve as the jet crashes and tells him to wait as she heads towards Ares. Diana is ambushed by Paula von Gunther but manages to defeat her with ease. Doctor Poison, watching from a distance, throws out a gas bomb which causes Diana to lose consciousness, and she is captured by Ares. Ares sucks Diana's soul out of her body and uses it to power the newly constructed machine. Steve reveals himself, and shoots at Ares, distracting him long enough for Diana's soul to return to her body. Diana stabs Ares with his own sword, impaling him against the machine and piercing it's plutonium core, causing a large explosion that levels the area. Diana and Steve get away unscathed.
As Diana and Steve recover from the battle, Doctor Poison attacks. Diana uses her lasso to grab a capsule off of Doctor Poison's belt and throw it back at her, releasing an acidic gas that kills her. Government agents arrive on the scene, and Steve jokingly calls Diana "Wonder Woman," just before the two share a kiss.
- Jaimie Alexander - Diana Prince / Wonder Woman
- Scott Eastwood - Steve Trevor
- Clancy Brown - General Wade Eiling
- Connie Nielsen - Queen Hippolyta
- Christoph Waltz - Ares
- Bridget Hodson - Baroness Paula von Gunther
- Elena Anaya - Doctor Poison
- Luke Bracey - David Trevor (young)
- Norman Lloyd - David Trevor (old)