Annaatthe (transl. Big Brother) is a 2021 Indian Tamil-language action drama film directed by Siva and produced by Kalanithi Maran under Sun Pictures. The film stars Rajinikanth in the titular role, alongside Khushbu, Meena, Nayanthara, Keerthy Suresh, Jagapathi Babu, Soori, Prakash Raj, and Abhimanyu Singh. D. Imman composed the film's music, Vetri handled the cinematography, Dhilip Subbarayan arranged stunts and Ruben edited the film. The movie's plot revolves around Kaalaiyan alias Annaatthe, a sarpanch (decision maker) in Thanjavur, who strives to protect his sister from an evil corporate and his crime boss elder brother in Kolkata.

The film was officially announced in October 2019, marking Rajinikanth's first collaboration with Siva. Principal photography began on 11 December 2019 and was completed in September 2021. The COVID-19 lockdown in India and Rajinikanth's health issues in late-December 2020 delayed the film's production. Filming was primarily done in Ramoji Film City, Hyderabad, and a few sequences were shot in Chennai.

Annaatthe was released on 4 November 2021, coinciding with the Deepavali festival. The movie received mixed reviews and was critically panned by critics. During its theatrical run, Annaatthe grossed an estimated revenue of ₹220-240 crores worldwide against a budget of ₹180 crores, making it an average grosser. The Embassy of India announced the release of the film in Argentina to promote culture and tourism.

Kaalaiyan is a sarpanch (decision maker) in the village of Soorakkottai, Thanjavur District, who respects the principles of fairness. His ideals lead him to clash with a rival village leader Nattadurai, who controls people by scaring them. When Nattadurai tries to extort land from an old man, he hires lawyer Pattammal to defend his case. Kaalaiyan exposes the truth, and Pattammal betrays her client and withdraws the case. Pattammal and Kaalaiyan fall in love. Kaalaiyan's world revolves around his sister Thanga Meenatchi, whom he raised after the deaths of their parents. Meenatchi returns home, having completed her education. Kaalaiyan has difficulty finding a husband for his sister because everyone is afraid of him. Kaalaiyan's annoying cousins, sisters Angayarkanni and Mangaiyarkarasi, both of whom wanted to marry Kaalaiyan but he had not agreed, propose their brothers marry Thanga Meenatchi. Without her consent, Thanga Meenatchi's marriage is arranged with Nattadurai's younger brother. Meenatchi goes missing on the day of the wedding; Kaalaiyan dispatches a search party who finds Meenatchi trying to elope on a train with her boyfriend from college.

Torn by his love for his sister, Kaalaiyan allows Meenatchi to leave and deflects demands from relatives for an honour killing. Meenatchi and her husband move to Kolkata, and she loses contact with Kaalaiyan. Kaalaiyan and Pattammal travel to Kolkata. Kaalaiyan discovers his sister has serious financial troubles; he secretly follows her and discovers that she has borrowed money from a gangster. When the gangster tries to assault Meenatchi, Kaalaiyan secretly assaults him and moves Meenatchi to Pattammal's apartment, where he can safely watch her. Thugs threaten Meenatchi, and she falls ill. When Pattammal leaves the house to get her medicine, the thugs attack her. Kaalaiyan rescues Meenatchi and interrogates her attackers.

When Meenatchi and her husband started a business in Kolkata, a wealthy businessman and underworld don Manoj Parekar approached them. Manoj wanted to purchase half of their shares, but Meenatchi's husband refused. Over the following weeks, Meenatchi's factory caught fire, they were forced to close it, and her husband was arrested on invented charges and tortured in police custody. Meenatchi had begged Manoj to get her husband released and signed over her company. Manoj had refused to get him released and had everyone who agreed to help her murdered.

In the present, Meenatchi is still trying to get her husband released with Pattammal's help and realises that she is pregnant. Kaalaiyan is very happy to hear this; he and Pattammal organise a baby shower for her. After learning about Meenatchi's misfortune, Kaalaiyan wants to kill the gangsters using his sister as bait and swears to destroy Manoj Parekar. Using the pseudonym Annaatthe, Kaalaiyan and his village friends storm Manoj's office and issue an ultimatum. After more drama, Annaatthe corners Manoj and forces him to sign papers saying he will return the companies he stole to their former owners. Kaalaiyan decides to spare Manoj's life. Enraged and humiliated, Manoj visits his estranged brother Udhav Parekar, where he demands the death of Annaatthe and then kills himself. Udhav finds Meenatchi and takes men to attack her. Pattammal, instructed by Kaalaiyan, hides Meenatchi. Udhav's men chase Pattammal and Meenatchi, who become separated by a crashing auto-rickshaw. Kaalaiyan arrives, assaults all of Udhav's men, and kills Udhav. Kaalaiyan reveals himself to Meenatchi, who tearfully apologizes for the trouble she put him through.

In mid-October 2019, media reports stated that Rajinikanth would be working with director Siva after the release of Darbar (2020). On 11 October, Kalanithi Maran, whose production house Sun Pictures was bankrolling the venture, confirmed the project, which had the working title Thalaivar 168. The project was Rajinikanth's 168th film. It was also Rajinikanth's third collaboration with Sun Pictures after Endhiran and Petta. Composer D. Imman, who had worked with the director on Viswasam (2019), was reported to be scoring for the film. His inclusion was confirmed by the producer in mid-November. It was reported that the film will be titled as Viyugam and Mannavan, however the team denied the rumours. The film's title Annaatthe was revealed on 24 February 2020.^{[excessive citations]}