Apurbo Kumar Roy (Apu) (Soumitra Chatterjee) is an unemployed graduate living in a rented room in Kolkata. Despite his teacher's advice to go to university, he is unable to do so because he can't afford it. He tries to find a job, while barely getting by providing private tutoring. His main passion is writing a novel, partially based on his own life, hoping to get it published some day. One day, he meets his old friend Pulu, who coaxes him to join him on a trip to his village in Khulna to attend the marriage of a cousin named Aparna (Sharmila Tagore).
On the day of the marriage, it is revealed that the bridegroom has a serious mental disorder. The bride's mother cancels the marriage, despite the father's protests. He and the other villagers believe, according to prevalent Hindu tradition, that the young bride must be wedded off during the previously appointed auspicious hour, otherwise, she will have to remain unmarried all her life. Apu, after initially refusing when requested by a few villagers, ultimately decides to take Pulu's advice and come to the rescue of the bride by agreeing to marry her. He returns with Aparna to his apartment in Calcutta after the wedding. He takes up a clerical job, and a loving relationship begins to bloom between them. Yet, the young couple's blissful days are cut short when Aparna dies while giving birth to their son, Kajal. Apu is overcome with grief and holds the child responsible for his wife's death.
He shuns his worldly responsibilities and becomes a recluse – travelling to different corners of India, while the child is left with his maternal grandparents. Meanwhile, Apu throws away his manuscript for the novel he had been writing over the years. A few years later, Pulu finds Kajal growing wild and uncared for. He then seeks out Apu, who is working at a mining quarry and advises Apu one last time to take up his fatherly responsibility. At last, Apu decides to come back to reality and reunite with his son. When he reaches his in-laws' place, Kajal, having seen him for the first time in his life, at first does not accept him as a father. Eventually, he accepts Apu as a friend and they return to Calcutta together to start life afresh.Soumitra Chatterjee as Apu (Apurba Kumar Roy)
Sharmila Tagore as Aparna, Apu's wife
Swapan Mukherjee as Pulu
Alok Chakravarty as Kajal
Sefalika Devi as Pulu's wife
Dhiresh Majumdar as Sasinarayan
Dhiren Ghosh as the landlord
Ray wanted fresh faces again for the film like other two films in the Apu Trilogy and thus he started auditioning. In others films he made in between, like Parash Pathar (1958) and Jalsaghar (1958), he did work with professional actors like Soumitra Chatterjee, a radio announcer and a stage actor who, with doyen of Bengali theatre Sisir Bhaduri, had first auditioned for the role of the adolescent Apu in Aparajito (1956). Though Ray thought he had the right look, he found him too old for the role. Ray remembered him and offered the role of adult Apu two years later. Chatterjee was still unaware that he had already been selected for the title role. He had gone on the sets of Ray's fourth film, Jalsaghar, to watch the shoot. That day, while he was leaving the sets, Ray called him over and introduced him to actor Chhabi Biswas, saying, "This is Soumitra Chattopadhyay; he's playing Apu in my next film Apur Sansar", leaving him surprised. Ray however had a tough time finding an actress for the female lead Aparna. He even placed an ad was placed in a local daily asking for photographs from girls between ages of 15 and 17. There were over a thousand responses to the ad, but Ray found none of them worth auditioning. This was when Ray came to know of a young girl, Sharmila Tagore, who had recently performed at a dance recital at Children's Little Theatre (CLT) in Kolkata. She is related to poet Rabindranath Tagore, and subsequently auditioned and was selected.
Despite being selected, as a debutant actor, Chatterjee was nevertheless unsure of his career choice and especially his looks, as he didn't consider himself photogenic. However, on 9 August 1958, when the first shot of the film was given an okay in one take, he realized he had found his vocation.National Film Awards (India)
Winner – 1959 – President's Gold Medal for the All India Best Feature Film
British Film Institute Awards (London Film Festival)
Winner – 1960 – Sutherland Award for Best Original And Imaginative Film
14th Edinburgh International Film Festival
Winner – 1960 – Diploma Of Merit
National Board of Review Awards (United States)
Winner – 1960 – Best Foreign Film 
British Academy Film Awards (United Kingdom)
Nominated – 1962 – BAFTA Award for Best Film
At Rotten Tomatoes, The World of Apu has a 100% fresh rating based on an aggregate of 21 reviews. In 1992, Sight & Sound (the British Film Institute's film magazine) ranked The Apu Trilogy at #88 in its Critics' Poll list of all-time greatest films. In 2002, a combined list of Sight & Sound critics' and directors' poll results ranked The World of Apu at #93 in the list. In 1998, the Asian film magazine Cinemaya's critics' poll of all-time greatest films ranked The Apu Trilogy at #7 on the list. In 1999, The Village Voice ranked The Apu Trilogy at #54 in its Top 250 "Best Films of the Century" list, based on a poll of critics. The film was selected as the Indian entry for the Best Foreign Language Film at the 32nd Academy Awards, but was not accepted as a nominee.
In 1996, The World of Apu was included in Movieline Magazine's "100 Greatest Foreign Films". In 2001, film critic Roger Ebert included The Apu Trilogy in his list of "100 Great Movies" of all time. In 2002, The World of Apu featured in "The New York Times Guide to the Best 1,000 Movies Ever Made". In 2005, The Apu Trilogy was included in Time magazine's All-Time 100 best movies list.
The World of Apu has been influential across the world. In Gregory Nava's 1995 film My Family, the final scene is duplicated from the final scene of Apur Sansar. The film's influence can also be seen in famous works such as Martin Scorsese's 1976 New Hollywood film Taxi Driver, several Philip Kaufman films, and Key's 2004 Japanese visual novel Clannad. References to The World of Apu are also found in several films by European filmmaker Jean-Luc Godard, and in Paul Auster's 2008 novel Man in the Dark where two characters have a discussion about the film.
The Academy Film Archive preserved the entire Apu Trilogy in 1996, including Apur Sansar.