The Duke and assorted senators of Venice are dealing with the impending war with the Turks over Cyprus, an island in the Mediterranean. The men compare conflicting reports of a Turkish fleet approaching the island, but are interrupted by a messenger, who says that, actually, the Turkish fleet is headed to Rhodes (yet another island, this one in between Greece and Cyprus).
After much quibbling, the men realize that the Turkish fleet sent to Rhodes was only a decoy, as Cyprus is more strategically important to the enemy. The governor of Cyprus, Montano, has sent a message from his location in Florence to confirm that his city is soon to be under siege: the Turks, with a fleet of 30 ships, really are headed for Cyprus, and he needs help from Venice – right now.
Brabantio enters the scene with Othello, Cassio, Iago, Roderigo, and a bevy of other officers. The Duke is quick to dispatch Othello to fight the Ottomans, but Brabantio pipes up. He says he hasn't come on matters of state, but rather because his daughter's been stolen.
The Duke says this is awful news, ignoring that this is probably not as awful as the fact that Cyprus is about to be pulverized by the Turks. Still, the Duke promises that whoever the man is that has enchanted Brabantio's daughter, even if it's the Duke's own son, he will get what's coming to him. Brabantio's quick to point out that the man is actually the Duke's current hero, the Moor, Othello.
The Duke asks Othello what he has to say for himself. Actually, Othello has quite a bit to say: his only offense is to have married Brabantio's daughter. Othello says he's a man of action, so his speech will be a poor defense, but he'll give them the whole story of how he won Brabantio's daughter, and they can then judge whether he's guilty or not.
Brabantio pipes up and insists that his daughter is as pure as the snow, so there's no way she could come to love the Moor except via his trickery. Othello begs to differ. In fact, he says, they can bring Brabantio's daughter, his new wife, to confirm the story right here and now, if they wish.
If Othello is in the wrong, the senators may take away his title and order him to be killed. Othello sends Iago, in whom he trusts, to fetch the girl while he tells the story of his courtship.
Othello explains that Brabantio himself used to invite him over all the time so he (Brabantio) could listen to the fantastic tales of Othello's life, including, but not limited to: daring escapes within a hair's breadth of death; being sold into slavery and getting his freedom back; and traveling over the world's caves, deserts, quarries, and hills. Also, there were cannibals.
Whenever Othello would come over, he noticed that Brabantio's daughter, Desdemona, would listen attentively whenever she could. Even when she had to tend to women's work, she'd sneak back to eavesdrop on the stories. Othello convinced Desdemona to ask him to hear his stories, which she clearly wanted to do. (Read that again, it's complicated, but it's important because it implies that their courtship doesn't seem to be one where one person was more actively pursuing the other.)
Othello then consented to tell her his stories and, upon hearing them, she swooned over Othello's daring. Desdemona then flirted with Othello, saying if he had a friend who could tell his stories (and had his bravery), she'd love that guy.
Othello takes the hint and says something like, "Well, I tell my stories pretty well, so maybe we should be friends." Othello claims Desdemona loves him for the dangers he had escaped, and he loves her for the pity with which she appreciates his dangerous escapes.
Just then Iago enters with Desdemona, the lady in question. Brabantio says he'd like to hear from his daughter whether she was willingly part of the courtship. He asks her where she thinks her loyalty should lie. Desdemona says she loves her father, but just like her mother, she must love her husband more than her father.
Brabantio is not pleased. He says he'll give Desdemona over to Othello, but still, Brabantio is an unhappy man.
The Duke says Brabantio would only waste his time being sad about what's already over. Besides his bitterness would likely only bring more trouble. Instead, he should just be happy because he doesn't have a choice but to be happy; he doesn't have a say in the affairs of his daughter anymore.
After Brabantio laments some more, the Duke gets back to the situation in Cyprus. Though they've already got some guys on the ground there, everyone would feel better if Othello went, as he's competent and knowledgeable about the area. The Duke says he's sorry, but Othello will have to spend his wedding night preparing for battle (not knowing he's speaking metaphorically and prophetically).
Othello says he's happy to go, but insists Desdemona should be taken care of, as with his wedding night interrupted, he hasn't been able to take care of her.
The Duke suggests that perhaps Desdemona should stay at her father's house, but everyone agrees this is a bad idea.
Instead, Desdemona suggests she'd like to go with her new husband. She suggests that her love is only complete if she can live with him. Desdemona says she fell in love with Othello's character and profession, and if she's left behind while he's in war, the very qualities she loves will be absent from her.
The Duke thinks they can settle these domestic disputes on their own. Whether Desdemona is to stay or go, Othello needs to leave for battle NOW. Othello agrees to this, and leaves his trusted friend, Iago, to follow, bringing Desdemona and anything else Othello might need.
As everyone is parting, the Duke tries to cheer Brabantio, saying Othello is "more fair than black." Brabantio won't have any of it, and warns Othello that he should watch the girl: she's likely to deceive him the way she deceived her own father.
Othello, in a moment of foreshadowing, responds that his life rests upon Desdemona's faithfulness. Othello instructs Iago to take Desdemona along with Iago's wife, Emilia, on the journey to the battle area.
After Othello and Desdemona have left, Iago remains with Roderigo. Roderigo announces he will drown himself out of lovesickness (for Desdemona), and Iago chides him for his foolishness. If he's going to be damned for some sin (like suicide), it would be better to be damned for a more practical one, like making money. Iago (who has been spending Roderigo's money like there's no tomorrow) instructs Roderigo to cool his passion with his reason. He then literally tells him nine times that he'd be better off focusing on making money than having true love.
Iago promises that once Desdemona passions for Othello will eventually cool. Othello will soon surely find he's had enough of Desdemona too, as Moors are known for their changing tastes. Then, Roderigo will have a chance to win Desdemona for himself.
Iago promises he'll join with the tribes of Hell to make trouble for the marriage of Othello and Desdemona, if Roderigo will only keep making money. Iago reminds Roderigo again that he hates the Moor, and promises to meet Roderigo in the morning, if he hasn't killed himself. Roderigo promises to sell all his land for money instead of killing himself. He then exits.
Once Roderigo's gone, Iago fills us in on his nasty plan. He's only sporting with Roderigo for fun and profit, but has a bone to pick with Othello, as it's rumored that Othello was sleeping with Iago's wife.
Iago then figures he'll take Cassio (his competitor) out, too. He hatches a plan to suggest to Othello that Cassio, who has the making of a ladies' man, is having an affair with Desdemona. Iago thinks the Moor is easily influenced, and his suspicion of Cassio will both ruin the great arithmetician's military career and Othello's marriage. Iago declares Hell and night will be his companions in this mischief, and he exits.