The play opens with the Chorus, a single character, who opens all five acts. He tells the audience to use their imagination and to think of the stage as the fields in France.

In the opening scenes, the Archbishop of Canterbury and the Bishop of Ely, both powerful men of the Church, are talking about a bill the young King Henry V wants to pass. The bill, although getting more money for the army and for the poor, would be cutting funds from the Church. Naturally, then, these two bishops don't want it to pass and think of a plan to divert Henry's attention away from the bill. The bishops know that Henry feels he has a claim to the French throne as well; therefore, they think if they can get Henry to start a war, then he would concentrate of the invasion of France over the bill. Canterbury helps to instigate this plan by offering the King a "donation" from the church to help fund the King's war efforts. In addition both bishops flatter the king saying he has changed dramatically since his youth. During his youth he had hung out with "low lifes" and was wild and reckless.

King Henry goes to talk to the ambassadors from France. His advisors and two of his younger brothers (the Princes Humphrey of Gloucester and Thomas of Clarence) are with him and he sends for the bishops. King Henry asks Canterbury to explain why the King of England should have claim to the throne in France. The explanation is complicated, but Henry is adamant that he wants full justification for starting a war. Canterbury tells him that in France, the throne can't be inherited through a mother. Therefore, daughters have no claim to the throne. This is the "Salic law" in France and England has no such law. Since King Henry's great-great-grandmother was a daughter of the King of France, under English law, than Henry would be the rightful heir to the French throne.

The French obviously don't agree and they already have a king, King Charles VI. All of the Kings advisors are now pressuring him to invade France. The King is worried since the Scottish rebels might invade while he is away. Canterbury then says that Henry should only take one quarter of his army with France, and the rest stay to defend England. King Henry agrees to the invasion of France.

King Henry goes to talk to the ambassadors and they laugh at King Henry's claim to the throne. They call the King too young to be responsible and then further insult him by offering him a gift of a barrel of tennis balls. Henry is enraged and declares his intent to invade and conquer France.

The Chorus introduces the second act informing the audience that England is preparing for war. Unfortunately the French have found some corrupt Englishman, Richard, Henry Lord Scroop, and Sir Thomas Grey, to agree to kill Henry in Southampton before he leaves for France.
In London, Lieutenant Bardolph and Corporal Nym are two "vulgar" commoners preparing for war. Before they leave, Nym gets into a quarrel with Pistol. Pistol has married Mistress Quickly, who previously promised to marry Nym. Pistol and Nym draw their swords and are quieted down by the Mistress and Bardolph. A boy, who is Sir John Falstaff's page comes to tell everyone Falstaff is very sick. The quarrel is then put aside and they all go to visit him. The men claim that King Henry has done something to cause, in some way, Falstaff's illness.

In Southampton, King Henry is preparing to sail to France and the conversation amongst the King's advisors reveals the planned murder. The traitors don't know yet. King Henry asks the traitors their advice on case in which a drunk man spoke badly of the King. King Henry says he wants to free him, but Cambridge, Scroop and Grey tell him to execute the man instead. King Henry decides to free the man and then tells the traitors he knows of their betrayal. They beg for forgiveness, but Henry reminds them that they would not pardon a drunkard. He executes all of them but is exceptionally upset that his lifelong friends would betray him for money. Nevertheless, he sees the events as a sign that God is on the side of the English.

In London, Pistol, Bardolph, Nym, and Hostess are grieving over the death of Sir John Falstaff. Before he died, in a delirious state, Sir John Falstaff said bad things about wine and no one can agree on whether he also cried out against women. The men are sad but still go off to war.
In France, the Charles VI and his nobles discuss Henry's might. Some feel he is strong; others think he is young and weak. Yet, they adequately prepare for the invasion especially considering the strength of Henry's predecessors. Exeter, an English nobleman, arrives to tell Charles that Henry is in France and will invade it if the throne is not handed over. Charles tells Exeter he will have an answer by the morning.

The Chorus appears to open the third act and describes how Henry landed with a large fleet of warships in France and has begun to attack the French city of Harfleur. Charles has offered the King a compromise: he will give Henry small dukedoms, but not the crown, and the hand of his daughter in marriage. Henry rejects this offer.

King Henry delivers a powerful speech in the midst of the fighting and the speech, the Chorus claims, effectively motivates the soldiers although Nym, Pistol, and the boy do voice that they would rather be in London. They are caught not fighting and an officer, the Welsh captain Fluellen beats them with a sword until they go back to fight. They boy remains back and reflects that these men are all cowards and he will look for a better job after the war.
Fluellen and Gower, another officer, discuss the strategy of the "mines" or tunnels that the English side is digging. Fluellen, who is well read in Roman war tactics, thinks they are being dug wrong.

Captain Macmorris and Captain Jamy enter and Fluellen offers Macmorris (whom he scorns) advice. They get into a quarrel, but end it since they realize there is a real battle going on.

The French town of Harfluer is under siege. King Henry tells the governor that if they surrender everyone will live. Otherwise they will destroy the town, rape the woman and kill the children. The governor does not want to surrender, but since he was heard from the Dauphin (the prince of France) that no army can be raised, he opens the gates.

In the next scene we meet Katherine, the King's daughter and her maid Alice for the first time. Much of this scene is in French since Katherine cannot speak English; Alice does know some. Katherine asks Alice to teach her English and she begins to learn the parts of the body. She mispronounces them and wants to learn until the two final words because they sound like obscenities in French.
The King of France is discussing the English victories with his nobles. Everyone is very upset and the French are shown as arrogant in this scene. They don't understand how people from such a cold climate (England) could be so hot-tempered and courageous. They are especially mad since their wives and mistresses have begun to make fun of them for losing. The king finally calls upon over 20 troops to be raised. He is now confident again that they will win.

Fluellen and another English captain, Gower discuss the right way to strengthen bridges. Ancient Pistol comes in and asks Fluellen to help him: Bardolph has been caught stealing a "pax" a tablet made out of valuable material for religious rites. Bardolph is sentenced to hanging. Fluellen won't help Pistol free Bardolph and Pistol curses Fluellen, gives him the finger and walks away. Gower tells Fluellen that Pistol is not even a real soldier, he just goes off to war when he wants to.

King Henry enters and learns that the English have won the bridge they were fighting for and that they have lost very few soldiers. He does not seem that upset that his friend, Bardolph will be executed, but he responds by saying that it is important to respect the French.

Montjoy is a French messenger and he comes to tell King Henry that King Charles will eventually punish him and he should start thinking about his "ransom".

King Henry replies in a surprisingly humble and even-tempered way. He claims his army is tired and he wants to avoid fighting, but will continue to march on.
At the French camp the Dauphin is bragging about his horse while the others teases him. Once they learn the English are close, they make fun of Henry.

The Chorus appears again to introduce Act IV. The French are over-confident since they outnumber the English 5 to 1. The English all believe they will die in battle but are pleased since King Henry went around during the night talking to each of them called, "a little touch of harry in the night". King Henry also talks to his brothers and asks to borrow Erpinghams's dirty cloak and then tells them to leave him alone.

Henry wraps himself in the cloak and pretends to be a soldier talking to anyone and they don't know he is the King. He firsts talks to Pistol who praises the King and gives him the fico. Next Fluellen and Gower walk by but they don't even see him. Fluellen scolds Gower for talking too loudly near the enemy camp and the King is proud of his intelligence. Three common soldiers: John Bates, Alexander court and Michael Williams all sit by Henry at the campfire and they talk about how they doubt the motives and courage of the King. Henry tries to defend the "king" but Williams won't back down and they quarrel. They exchange gloves to signify their intent to fight. Henry is now alone, it is almost daybreak, and he thinks about the responsibilities of being a king. He then prays for a victory and repents the bloody way in which his father got the crown.
All the while the French are looking forward to an easy victory.

The English hear that they are outnumbered 5 to 1 and are intimidated and upset. Henry then gives his famous, "St. Crispins's Day Speech" in which he claims they should be happy there are less of them, since there is a greater share of honor. He also tells them that if they don't want to fight, then they should leave - he will even give them money to go home. In addition, he goes as far to claim that any commoner who fights today will symbolically become the King's brother. The soldiers are greatly inspired.

Montjoy comes to the English camp to see if they will surrender instead of facing defeat. Henry rejects him courteously and the battle begins. Pistol takes a French prisoner and they humorously try to communicate; Pistol is mistaken for a nobleman. The Frenchmen, who calls himself Monsieur le Fer says he is from a respected house and will give Pistol a lot of money if he frees him and Pistol accepts. The boy, seeing all of this is every upset, especially since Nym, like Bardolph was just executed for stealing.

The English have, unexpectedly won the battle, and the French troops are shocked. The French debate suicide but end up continuing to fight in the Battle of Agincourt.

Exeter reports that the English are winning but both the Duke of York and the Earl of Suffolk are dead. They died side by side together. Henry is moved by the story are cries.

The French have looted the English camp and killed their pages. Henry orders all the French prisoners to now be killed. Fluellen and Gower discuss this action by the French and are extremely upset with them for acting so unchivalrous. They both approve of Henry's decision. Henry is compared to Alexander the Great.

Montjoy comes in to report that the French want to bury their dead and Henry asks him if the English have won. Montjoy says they have. Henry sees Williams (the soldier with whom he exchanged gloves) and plays a practical joke. He gives the glove to Fluellen and has him wear it and say it came from a Frenchmen on the field and that anyone who attacks Fluellen must be a traitor to the English. Williams sees Fluellen and strikes him and Fluellen orders his arrest. Henry innocently asks what happened and then he reveals the truth to Williams about his disguise the night before. Williams says that he cannot be blamed for the trick and the King rewards his bravery by filling the glove with gold coins. 10,000 French are dead while only 29 Englishmen have been killed. The English praise God.

The Chorus introduces Act V, the last act. We learn Henry had returned to Calais in France and then sailed back to England. People flock to him once he returns, yet the humble King does not march in a triumphant procession. The King must return to France soon and with him he brings Gower and Fluellen. Gower asks Fluellen why he wears a leek in his hat and he claims St. Davy's Day was the previous day and that Welsh people wore a leek in their hats to show pride. A leek is a large scallion like vegetable. Pistol, Fluellen explains, had insulted him for wearing the leek and sent him bread and salt and told him to eat his leek. Fluellen begins to beat up Pistol and finally tells him he has to eat the leek. Pistol does, but vows for revenge. Gower reminds Pistol it was his own fault for making fun of him for being from a different culture. Once alone, Pistol tells the audience his wife has died of a venereal disease, he no longer has a home, and he will become a "bawd", pimp, and a thief in London to survive.

In France, King Henry comes to meet Charles and the Queen of France, Isabel. Even though he won, Henry will let Charles keep his throne. In addition he wants to marry Katherine.
Henry and Katherine are now alone in the room together and Alice comes to translate. This is a comic scene in which Henry courts Katherine using bad French and mostly English. Katherine agrees, everyone else comes back in (Henry and the Duke of Burgundy talk about what Katherine would be like in bed) and the treaty is signed.

The Chorus appears to end the play. We learn of the birth of Katherine and Henry's son, King Henry VI of England who loses the French lands and brings England to war.