IMDb; Lionsgate; Sonar Entertainment; Wikipedia
Amphitryon, a noble warrior of Thebes, returns from war to find his wife, Alcmene (who we like). She and her family worshipped Hera, while Amphitryon worships Zeus. (Alcmene is Hera's high priestess.) And of course, Zeus and Hera are at war with each other. The whole movie is about the war between them, although we never actually see either of them. In fact, there never seems to be any absolute proof they even exist (which seems pointless, since despite any evidence of gods, there are plenty of mythological creatures, such as nymphs, satyrs, centaurs, a hydra, a sphinx, harpies, etc.), but that doesn't stop their respective followers from doing all sorts of terrible stuff in their names. Anyway, Alcmene doesn't really want to be with Amphitryon, but has no choice. And the night his ship returns, she's raped by someone, who she at first thinks is him, but later believes to be Zeus. Turns out Amphitryon was on his ship all night, and the next day... he's with Alcmene. She later bears two sons, Iphicles (Amphitryon's son), and Hercules (Zeus's son). She wants nothing to do with Hercules, wants him dead. But Amphitryon won't kill the son of his god. (Toward the end of the movie, it is suggested that Zeus isn't actually his father, it's maybe someone else, but I won't say who.)
Anyway, one day Hercules and Iphicles are being taught music and biology by a poet named Linus, and Hercules seems to kill Linus, accidentally. For this, he is banished from Thebes; though later Linus is revived by a nymph named Deianeira (who we quite like). Eventually, Hercules will fall in love with her, and Linus will become his faithful sidekick and write songs of his adventures. But anyway, one night Megara (who we like), daughter of King Creon of Thebes (and also a priestess of Hera) has sex with Hercules, but later claims he raped her. She also bears Hercules three sons, who hate him. Later he saves the king, and all Thebes, when he slays the hydra (in a battle which claims the life of Amphitryon). The king gives him Megara to wed, as a reward. Alcmene, Megara, and Iphicles plot together against Hercules (though eventually they'll all betray each other in various ways). They trick Hercules's sons into trying to kill him, disguised as demons, after Megara has drugged him, thus tricking him into killing them.
The king sends him to the oracle at Delphi (who turns out to be Tiresias, an important player in the whole story, from beginning to end) to find a way to atone for his crime, and the oracle says he must perform five labors for King Eurystheus of Tiryns (son of the late Sthenelus, a usurper who had killed Alcmene's family, though he was also her uncle). Eurystheus is now married to Megara (their marriage united Thebes and Tiryns; they had been engaged prior to Hercules slaying the hydra). So he goes off and does each task set to him, fighting monsters and whatnot, which Megara and her cohorts hope will destroy him. Each time he wins his battle. One of these battles is against a bandit named Antaeus, who kills Hercules's centaur friend, Kiron. Actually, two of the battles are against him.
Anyway... the people of Tiryns get to like Hercules more and more, with each victory. And he has a son named Hyllus with Deianeira, and Hercules wants him to marry Megara and Eurystheus's daughter Iole, but no one else seems to want that. And lots of other stuff happens, including a big melee, and eventually Hercules and Deianeira get married by Linus. And Hercules hopes Zeus and Hera can learn to love each other. The end. I'm probably forgetting some important details or maybe mixing some things up. It was all rather complicated, and I don't think it followed proper mythology all that well. Nevertheless, I found it reasonably enjoyable, I guess. ...But looking back on it all, years later, I basically remember none of this. The only thing I actually recall (vaguely) is that Deianeira was played by Leelee Sobieski. Looking at a list of stars, I'm sure when I watched it I was familiar with Timothy Dalton (Amphitryon) and Sean Astin (Linus) and Elizabeth Perkins (Alcmene), but now I don't actually remember them being in this.