The King and I is a film adaptation of the Rodgers and Hammerstein musical.
- Marni Nixon - Anna Leonowens (singing voice)
- Yul Brynner - King Mongkut
- Leona Gordon - Tuptim (singing voice)
- Terry Saunders - Lady Thiang
- Rex Thompson - Louis Leonowens
- Rueben Thuentes - Lun Tha (singing voice)
- Deborah Kerr - Anna Leonowens
- Rita Moreno - Tuptim
- Martin Benson - The Kralahome
- Carlos Rivas - Lun Tha
Strong-willed, widowed schoolteacher Anna Leonowens arrives in Bangkok from Wales with her young son Louis after being summoned to tutor the many children of King Mongkut. The two are introduced to the Kralahome, King Mongkut's confidante and Siam's prime minister. His severe countenance makes Louis apprehensive, but Anna refuses to be intimidated and convinces him to disguise his fear. The Kralahome explains he has come to escort them to the Royal Palace where they will live – a violation of Anna's contract, which calls for them to live in a separate house outside the walls of the palace. Despite her threat to return to Singapore, Anna reluctantly disembarks with Louis and the Kralahome.
Once inside the Royal Palace, Anna demands to see King Mongkut and is allowed by the Kralahome to enter the Throne Room. A pleased Mongkut ignores her objections as he introduces her to his numerous wives – who include head wife Lady Thiang and a graceful girl from Burma named Tuptim. King Mongkut later presents the fifteen children she will tutor, aside from the other sixty-seven - among them his eldest son and heir Prince Chulalongkorn. Anna eventually agrees to stay and tutor the King's children, prompting formality to break down. Later that night, Lady Thiang and the other wives assist Anna in unpacking while also interested in how the British dress and act. When an old photograph of her late husband Tom is discovered, the wives start to deride the unhappy Tuptim because she is in love with another man named Lun Tha, the same man who brought her to Siam. This causes Anna to reminisce about her life with Tom and give her blessing to other girls who are like she once was.
Anna refuses to give up on the house and teaches the children about the virtues of home life to King Mongkut's irritation. The King contemplates how he craves truth and wonders why the world has become so complicated with different cultures saying different things. Meanwhile, Anna shows the children a modern map – saying that England is even smaller than Siam. Anna starts to form a relationship with the children as getting to know people is her favorite thing to teach. The lesson, however, creates disorder when the children refuse to believe in snow. The King eventually enters a chaotic schoolroom, ordering his pupils to believe Anna. Upon noticing Tuptim has a copy of the novel Uncle Tom's Cabin, he engages in a slightly heated conversation with Anna about slavery – an institution embraced by all his people.
That night, Anna is summoned to the King's private chambers where he says that after reading the Bible, he believes that the world was not created in six days, but after many centuries. The King disregards her explanation and orders her to take a letter to President Abraham Lincoln, in which he will send male elephants to America to help with the Civil War. He then forces her to sit on the floor due to an ancient custom that no one's head should be higher than his. She then continues to write the letter, but is left to finish the letter herself when she tries to explain that the elephants will not last long if only male elephants are sent. Anna goes outside, only to come across Lun Tha and learn that he has been meeting Tuptim in secret. He asks her to arrange a rendezvous and she refuses out of fear but eventually relents after remembering her past with her Tom. The lovers meet under the cover of darkness and Lun Tha promises he will one day return to Siam and they will escape together.
The next day, King Mongkut becomes troubled by reports of English imperialism and bursts into the schoolroom after hearing Anna's pupils persist in singing "Home Sweet Home." Anna stands her ground, threatening to leave Siam despite pleas from the children. King Mongkut asserts that Anna is his servant only to see her repudiate the term and leave the room. King Mongkut then dismisses school and contemplates his next action. Lady Thiang visits Anna later that night and explains Mongkut is apprehensive over rumors that the British regard him as a barbaric leader, intending to turn Siam into a protectorate. Anna is shocked by the accusations but is reluctant to give him advice after their argument. Lady Thiang convinces her that the King is deserving of support and convinces Anna to go to the King. Anna learns the King is also anxious for reconciliation and learns that the British are sending an envoy to evaluate the situation in Bangkok. Upon learning that the envoy consists of Ambassador John Hay and her old lover Sir Edward Ramsay, Anna persuades the King to receive them in European style by hosting a banquet with European food and music – after which it is announced that the envoy is arriving in one week. The King assembles his family for a Buddhist prayer for the success of the venture and promises to give Anna a house of her own.
On the night of the banquet, The King has the wives wear lavish European-style gowns, but Anna discovers in horror they are not wearing undergarments. She entreats the women to keep their backs to the wall as Ambassador Hay enters the room. But the ladies flee the room in horror at the sight of the Ambassador's monocle, coming to the conclusion that he has an evil eye and the head of a goat on the matter of his beard. Ambassador Hay is diplomatic about the incident and follows the King into the Dining Room as Edward reminisces with Anna about old times in an attempt to bring her back to British society. The King however walks in on them dancing and irritably reminds them that dancing is for after dinner. After impressing the guests with his intellectual observations, the King presents Tuptim's version of Uncle Tom's Cabin – which is presented as a traditional Siamese ballet. However, the King and the Kralahome are not impressed as the play involves the issue of slavery and shows the slaveholding King dead after drowning in the river. By the time the audience calls for the play's author, Tuptim has left the room to meet with Lun Tha.
After the guests have departed, Anna talks with the King and is presented with one of his rings in appreciation of her efforts. He then explains he is not pleased with Tuptim and reveals she is missing. Anna however parries his inquiry by explaining she is unhappy because she is just another woman in his eyes. The King retorts that men are entitled to a plentitude of wives although women must remain faithful, explaining in a poem that men are "like honeybees" gathering honey from "blossoms," while "Blossoms must never fly from Bee to bee to bee". Anna explains the reality of one man loving only one woman and recalls her first dance before teaching the King how to dance the polka. But the touching moment is shattered when the Kralahome bursts into the room with news that Tuptim has been captured. For her dishonor, the King prepares to whip her despite Anna's pleas. She implies that he is a barbarian with no heart and that she will stay watch the King's actions. The King then crumples, puts his hand over his heart and runs out of the room. The Kralahome blames Anna for ruining him and now he can never be the king he was before. Tuptim meanwhile is led away in tears when she learns that Lun Tha is dead, his body discovered floating in the river. This causes Anna to return the ring, sever all ties as a governess and leave on the next boat from Siam.
On the night of her departure, Anna is prepared to leave Siam with Louis when Lady Thiang says that the King is dying. He refused to eat or sleep, isolating himself from everyone since the night of the banquet. Lady Thiang gives Anna an unfinished letter from the King that states his deep gratitude and respect for her, despite his harsh differences with her. This prompts her to go to his bedside in tears moments before their ship departs for Wales. The King gives Anna his ring, insisting that she wear it as she has always spoken the truth to him, persuading her and Louis to stay. King Mongkut then passes his title to Prince Chulalongkorn, who then issues a proclamation that brings an end to slavery and state that all subjects will no longer bow down to him. Satisfied that he is leaving his kingdom in capable hands, the King quietly dies with only Anna and the Kralahome noticing.
- "I Whistle a Happy Tune" - Anna and Louis
- "Hello, Young Lovers" – Anna
- "A Puzzlement" – The King
- "Getting to Know You" – Anna and Chorus
- "We Kiss in a Shadow" – Thiamin and Lun Tha
- "Something Wonderful" – Lady Thiang
- "Finale, Act I" – The King and Chorus
- "Song of the King" – The King
- "Shall We Dance?" – Anna and The King
The following songs were cut from the final film:
- "My Lord and Master" - Thiamin
- "I Have Dreamed" - Thiamin and Lun Tha
- "Shall I Tell You What I Think of You?" - Anna