The Lunchbox is a 2013 drama film written and directed by Ritesh Batra. Produced by Guneet Monga, Anurag Kashyap and Arun Rangachari, The Lunchbox is an international co-production of studios in India, the US, Germany and France. It stars Irrfan Khan and Nimrat Kaur alongside Nawazuddin Siddiqui, Bharti Achrekar and Nakul Vaid in supporting roles.

The Lunchbox was screened at Critics' Week at the 2013 Cannes Film Festival, and later won the Critics' Week Viewers Choice Award also known as Grand Rail d'Or. It was shown at the 2013 Toronto International Film Festival. The film was released in theatres in India on 20 September 2013. The Lunchbox was a box-office success and received unanimous critical acclaim. It was Khan's highest-grossing Hindi film, until it was surpassed by Hindi Medium (2017). The Lunchbox was nominated for Best Film Not in the English Language at the 2015 British Academy Film Awards.

Ila (Nimrat Kaur) is a young housewife seeking the attention of her husband, Rajeev (Nakul Vaid), and searching for ways to bring the romance back into her marriage; one of her ideas is to cook delicious lunches for him. Through a rare mix-up of the dabbawalas (a complicated food delivery system in Mumbai that picks up and delivers lunches from restaurants or homes to people at work), the tiffin carrier (lunchbox) Ila prepares for her husband gets accidentally delivered, instead, to Saajan Fernandes (Irrfan Khan), a middle-aged widower who is about to retire from his job of an accountant. Ila eventually realises the mistake and with the advice of her neighbour aunt, Mrs. Deshpande (Bharti Achrekar - voice only), living in the apartment above her, writes a letter to Saajan about the mix-up and places it in the lunchbox (along with her husband's favourite meal) the next day. An exchange of letters sent back and forth with the lunches ignites a friendship between the two, as they share memories and events from their own lives.

At work, Saajan is tasked with training his replacement, Aslam Shaikh (Nawazuddin Siddiqui). Socially distant after his wife's death, Saajan is initially reluctant to interact with Shaikh and train him. After Shaikh reveals that he is an orphan who taught himself accounting, Saajan gradually warms up to him, and eventually the duo strike a close friendship. At one point, Saajan saves Shaikh's job by covering for his blatant mistakes and becomes the best man at his marriage with Mehrunissa (Shruti Bapna). Meanwhile, Ila discovers that Rajeev is having an extramarital affair and gives up hope of rekindling her marriage. In one of the lunchbox letters, she suggests moving to Bhutan where the cost of living is much cheaper than India. Saajan writes back with the suggestion that the two move there together. Ila then offers to meet in person at a popular restaurant but at the appointed time, Saajan does not show up. Upon receiving an empty lunchbox in disappointment the next day, Saajan writes back to the dejected Ila and apologises to her, stating that he did arrive and watched her from a distance, but could not approach her. He explains how young and beautiful she looked, while surmising that he is too old for her and advising her to move on.

Some time later, Ila's father, battling lung cancer, dies in the care of her mother (Lillete Dubey), who confesses how unhappy her marriage was. She gives Ila the advice “Sometimes, the wrong train takes us to the right station”. Ila receives the address of Saajan's office from the dabbawalas only to learn from Shaikh that he has already retired and headed to Nashik. She writes a farewell message to Saajan announcing that she has decided to leave Rajeev and move to Bhutan with her young daughter, Yashvi. Meanwhile, Saajan changes his mind en route to Nashik and returns to Mumbai. The film ends with Ila waiting for Yashvi to return from school and Saajan heading to her house with the dabbawalas who regularly picked up and delivered the eponymous lunchbox.

Ritesh Batra, who had made the short films The Morning Ritual, Gareeb Nawaz Ki Taxi and Cafe Regular, Cairo, started researching a documentary on the famous dabbawala Lunchbox delivery system of Mumbai which is known for its efficiency, however after spending a week with them in 2007, he heard many interesting personal stories the workers would overhear while waiting outside apartments. This experience birthed the idea for the film, and instead of making a documentary, he began writing a film script. In time the film became a joint production between Sikhya Entertainment, DAR motion pictures, National Film Development Corporation of India (NFDC), India, ROH Films, Germany, ASAP Films, France and the Cine Mosaic, a production company based in New York City and founded by Lydia Dean Pilcher who had previously produced films such as The Talented Mr Ripley (1999) and The Namesake (2007). Germany's Match Factory became its international sales agent.

Batra completed the first draft of the screenplay in 2011. He was assisted by Rutvik Oza. It went on to win an Honorable Jury Mention at the 2012 Cinemart at the Rotterdam International Film Festival. Thereafter the project was part of the Talent Project Market of Berlin International Film Festival and was mentored at the screenwriter's lab (Torino Film Lab) at the Torino Film Festival. The character of Ila played by Nimrat Kaur, six months prior to the shooting, and the character played by Nawazuddin Siddiqui was further developed and improvised during shooting.

Irrfan Khan liked the script of the film and the concept of his character, not speaking much but talking through notes. After seeing Batra's short film and having a couple of meetings he agreed to act in the film. Batra wanted to work with Nawazuddin Siddiqui, another principal character in the film, for a long time. For the female lead, auditions were conducted, wherein Nimrat Kaur was selected. Kaur had extensive experience at the Mumbai theatre and had worked in films like Peddlers. Some of the dabbawalas whom the director befriended while researching the film were also cast in minor roles.