In Kolkata, prisoner Kathiresan "Kathir" (Vijay), a petty criminal, helps the police capture an escaping prisoner Vivek Banerjee (Tota Roy Chowdhury), but he himself escapes afterwards. He goes to Chennai and decides to escape to Bangkok with his friend and fellow-criminal Ravi (Sathish). However, he drops this plan after meeting and falling in love with Ankitha (Samantha Ruth Prabhu) at the airport, who dupes him into believing that she wants to marry him after realising that he is having a crush on her. Later, Kathiresan and Ravi notice a doppelgänger of Kathiresan named Jeevanandam "Jeeva", being shot by a group of thugs. They admit him to a hospital, following which Kathiresan decides to impersonate the injured Jeevanandam to escape from the police. Under the name of his doppelgänger, Kathiresan and Ravi enter an old-age home run by Jeevanandam with the aim of collecting ₹25 lakhs (which is meant for the inmates of the old-age home) for their Bangkok trip, until he learns about his doppelgänger's mission. Jeevanandam is a communist ideologue and a post-graduate in hydrology from the arid village of Thanoothu in Tirunelveli district who had discovered groundwater under some lands of the village which could be used as an irrigation source not only for the village, but for the entire Tirunelveli district and the neighbouring Thoothukudi district as well. But, an MNC owned by Chirag (Neil Nitin Mukesh) cheated the villagers into giving their lands for the construction of a factory. Jeevanandam was arrested by the police and the six villagers as for convince the issue with media and release of Jeevanandham commit mass suicide. On learning of the plight of Jeevanandam and the villagers, Kathiresan decides to fight for their cause while still under the name of Jeevanandam. The people of the old home and Kathiresan go to the jury and try to convince him to go in favour of them, but Kathiresan starts stating rules and scares the main jury person (whom Chirag had bribed). Kathiresan then sends a person (disguised as a hairdresser) to Chirag and makes him lay a fingerprint on Chirag's neck. After that Chirag sends 50 men to kill Kathiresan but he soon defeats them using the coins the villagers gave when he was attending a ceremony for him.
Meanwhile, the real Jeevanandam gains consciousness and finds himself in the Kolkata prison where Kathiresan was locked up. With the help of Vivek, who has heard his story and has plans to kill Kathiresan in revenge for getting him caught and thrown back into prison, he soon escapes along with Vivek's henchmen.
Not knowing that Jeevanandam and Vivek's henchmen are headed for Chennai, Kathiresan makes efforts to convince the media to bring the plight of the villagers to national consciousness, but the media is not interested as they feel that it is not a sensational news. A few days later, at the Madras High Court, the judge declares the verdict in favour of Jeevanandam and the villagers, but adds that Chirag has claimed that certain villagers who are working abroad have shown their support for the factory. If they cannot prove that their support was faked by Chirag within the next five days, the verdict will then go in favour of Chirag and the villagers will lose their lands. Since the villagers, who have denied supporting the factory, are abroad and cannot come to Chennai within five days to rebut Chirag's claims as their passports are held by their contractors, and the verdict is to be decided within five days, Kathiresan decides to take drastic measures to sensationalise the issue. He, Ankitha, Ravi and the inmates of the old-age home block water supply to Chennai by sitting on the pipelines which carry water to Chennai from five lakes. With the plight of the Chennaites due to no water supply having gained national attention, Kathiresan comes out of the pipeline after a few days and highlights the villagers' plight in an emotionally charged speech to the media, which is telecast nationwide and moves many people. By now, Kathiresan has discovered that Jeevanandam has escaped and is searching for him.
Meanwhile, Jeevanandam and Vivek's henchmen reach Chennai, but Jeevanandam is soon kidnapped by Chirag's henchmen. While in Chirag's custody, he sees Kathiresan's speech on television and is moved by the efforts made by his doppelgänger to help the villagers. On the night before the verdict, Kathiresan's bluff is exposed, but Kathiresan assures the old men that he is genuinely interested in their cause, that Jeevanandam is alive and that he will rescue Jeevanandam from Chirag and hand him back over to the villagers with the assurance of a positive verdict. Kathiresan goes to Chirag's office, where Jeevanandam is being held. He rescues Jeevanandam and fights Chirag and his henchmen, killing Chirag in the process.
The next day, the verdict is declared in favour of Jeevanandam and the villagers. Kathiresan, despite his efforts to thwart Chirag and the MNC, does not take part in the ensuing celebrations over the verdict and instead surrenders to the police and returns to the Kolkata prison, but not before promising Ankitha, who has now fallen in love with him, that he will marry her once he is released.Vijay as Kathiresan/JeevanandhamNeil Nitin Mukesh as ChiragSamantha Ruth Prabhu as AnkithaTota Roy Chowdhury as Vivek BanerjeeSathish as RaviYuvina Parthavi as Ankitha's nieceSudip Mukherjee as Kolkata police inspectorJeeva Ravi as CollectorRama as Jeeva's motherRupesh GuptaVeera SanthanamTamiko Brownlee as JenniferElisabeth P. Carpenter as KatherineAR Murugadoss in a cameo appearance
In 2012, it was reported that Murugadoss and Vijay would work together again. Murugadoss confirmed the same on his Twitter page. According to sources, the film was not a sequel to Thuppakki. Ayngaran International and Lyca Productions were confirmed to be the producers and distributors of the film. Murugadoss replaced his usual music director Harris Jayaraj with Anirudh Ravichander and signed George C. Williams as the cinematographer, who had filmed Raja Rani, (2013) which was produced by Murugadoss himself. Art director Lalgudi N. Ilayaraja, who had won the National Film Award for Best Production Design in Vishwaroopam (2013), was selected to handle the art direction for the film. The film was earlier rumoured to be titled as Dheeran. Another potential title for the film was Vaal. In March 2014, Murugadoss confirmed that the film would be titled Kaththi and that it was scheduled to be released on Deepavali.
In September 2013, Samantha Ruth Prabhu was selected as the lead female lead. Bengali actor Tota Roy Chowdhury was signed for portraying the antagonist role, an international gangster named Vivek Banerjee. In March 2014, Bollywood actor Neil Nitin Mukesh was selected to be a part of his project, thereby making his début in Tamil cinema through the film. Murugadoss also stated that Vijay would play a dual role. Sathish was chosen to play a supporting role. Sayaji Shinde and Subbu Panchu were selected to play pivotal roles in the film.
Neil was inspired by his look in his début film, Johnny Gaddaar (2007). He described his character as one who does not "fight the hero with physical power, but with intelligence". He learned Tamil for his role, as he did not want to speak his dialogues without understanding their meaning. Neil had lost weight for the role and modelled his looks to be along the lines of Brad Pitt and David Beckham.
The film was launched in Kolkata on 3 February 2014 by its producers Ayngaran International with a pooja ceremony in front of the Kalighat Kali Temple, after which principal photography began. The first schedule of filming was done on Kolkata and Hyderabad. In between, Murugadoss, took a break to promote his then upcoming Bollywood film, Holiday: A Soldier Is Never Off Duty (2014), the Hindi remake of Thuppakki (2012). The film was then shot in Pushpa gardens in Chennai, where a huge set which costed around ₹12.5 million (US$190,000) was erected and most of the indoor scenes were completed in this set. Shooting continued for a 40-day-long schedule in and around the city. By July 2014, 60% of the shooting had been completed and the team shot a few scenes in Kadapa. The final leg of the film began on 1 August 2014 at Chennai.
In late August 2014, 15 days of filming, including patch-work and a few fight sequences, remained. Filming moved back to Hyderabad, where the rest of the fight sequences were canned. On 1 September 2014, the second half of the film was nearly completed. Additional filming took place at the Chennai Central railway station. On 4 September 2014, Neil Nitin Mukesh dubbed in Tamil himself for his role and completed his dubbing portions for the first half of the film. The climax sequences were shot in Nellore on 23 September 2014. The song "Selfie Pulla" was shot in Mumbai. About 100 dancers participated in the song sequence. Filming of the song was completed on 30 September 2014, with the filming of the entire film also being completed as a result.
The soundtrack album and background score were composed by Anirudh Ravichander. The soundtrack album consists of seven tracks. The audio launch took place on 18 September 2014, at The Leela Palace Hotel in Chennai. On 29 January 2015, to celebrate 100 days of Kaththi, the crew released the background music in a jukebox format on YouTube.
The satellite rights of the film were sold to Jaya TV. T. Shibu of Thameens Films promoted and distributed the film in Kerala. The theatrical rights in Tiruchirappalli and Thanjavur were sold to T. Siva. Producer Tagore Madhu bought the film's Telugu dubbing rights. MM Media, previously known as GK Media, acquired the film's theatrical rights in the USA. The film released worldwide on 22 October 2014.
The 41-second first-look motion poster drew comparisons with the popular minute-long advertisement campaign run by a Turkish newspaper, Sabah, to announce their distribution of the New York Times as a supplement. The original advertisement features iconic images of the cities of New York City and Istanbul, designed using news articles and headlines from the newspaper to show the two cities in the form of newspaper clippings. The motion poster of the film showed prominent places in Chennai and the entire city itself in the form of newspaper clippings and headlines, just like the advertisement campaign, without an acknowledgement to the makers of the original.
Minjur Gopi filed a case against Murugadoss, claiming that the plot of the film was copied from his novel Mootha Kudi. Responding to the issue, Murugadoss said that he was neither aware of Minjur nor that his story was a copy, further citing the allegation as a tactic by the plaintiff to garner free publicity. He, in turn, requested the court to dismiss the petition. In late September 2014, the court declared the case in Murugadoss's favour, citing lack of proper evidence found against him.
Subaskaran Allirajah, chairman of Lyca Mobiles, whose company Lyca Productions co-produced the film along with Ayngaran International, was claimed to have had business links with the President of Sri Lanka, Mahinda Rajapaksa. Murugadoss and Karunamoorthy of Ayngaran International met pro-Eelam leaders — Pazha Nedumaran, director Seeman and Viduthalai Chiruthaigal Katchi's (VCK) Thol. Thirumavalavan — to explain their position regarding the allegation, but the talks proved to be inconclusive at that time. A collective of four student bodies — Maatram Maanavar Ilaiyor Iyakkam, Free Tamil Eelam Students Organisation, Tamil Youth and Students Association, and Progressive Students Front — in Tamil Nadu called for a ban on the film, stating that the film promoted the economic and political interests of Sri Lanka. The students were willing to reconsider their position on the film if Lyca Productions formally withdrew as producer. In August 2014, directors Seeman and Vikraman showed support for the film.
Despite clarifications, as many as 65 Tamil groups came together to oppose the film, leading to speculations regarding Lyca stepping down as producer and handing the reins to another production group. Karunamoorthy, however, again denied that Allirajah had business links with either Mahinda Rajapaksa or his family in any way, further saying that a press meet would be held where all doubts and suspicions regarding Lyca Productions would be clarified and that the film would be released under the Lyca Productions banner.
As per Karunamoorthy's statement, a press meet was held on 16 September 2014, where the vice-chairman of Lyca Productions, Premananthan Sivasamy, Subaskaran and Karunamoorthy were present. A statement with a detailed clarification was shown in which it was mentioned that Lyca did not have any business links with Rajapaksa or anyone else related to him, thereby confirming the planned release of the film on Deepavali.
Kaththi opened to mostly positive reviews from critics. Behindwoods gave it 3 out of 5 and stated, "Murugadoss delivers a strong commercial movie with a nice social angle, in true Vijay style". Sify gave it 4 out of 5 and stated, "the movie is a well made entertainer with a powerful message". M. Suganth of The Times of India gave it 3 out of 5 and wrote, "Kaththi will definitely be picked up by a big Bollywood star for a remake, for the knife was bang on target".
International Business Times gave the film 4 out of 5 and stated, "Kaththi is a message-oriented and highly entertaining commercial movie". S. Saraswathi of Rediff stated, "Kaththi entertains with a message" and rated it 4/5 as well.
Kaththi netted around ₹125 million (US$1.9 million) in Tamil Nadu alone. It grossed around ₹238 million (US$3.7 million) wordwide on its opening day and ₹710.5 million (US$11 million) worldwide in its extended five-day weekend. In Chennai city alone, the film netted ₹30.1 million (US$470,000) in the first week with an average theatre occupancy of 97% and stood in the first position. The second week witnessed an occupancy of 85% in the city and netted around ₹53.24 million (US$830,000). The film took a worldwide distributor share of ₹620 million (US$9.7 million) in just 11 days. The film still stood at the number one position in Chennai by the third week resulting in a total collection of ₹6.798 crore (US$1.1 million). Kaththi reached the ₹1 billion (US$16 million) mark in 12 days of its release. The film was bought for a record price in Karnataka by a leading distributor, and opened well at the box-office there. The film collected around ₹360 million (US$5.6 million) in Tamil Nadu, ₹50 million (US$780,000) in Karnataka and ₹55 million (US$860,000) in Kerala in five days. After a long run for nine weeks at the Chennai box office, the film netted around ₹78.29 million (US$1.2 million). Kaththi completed a 100 days theatrical run on 29 January 2015.
The film earned $142,805 in its USA premiere. In France, Kaththi opened with about ₹3.1 million (US$48,000) which is a new record for an Indian film. The distributor Ayngaran International stated that Kaththi had the biggest opening for a Tamil film in UK since it released in over 70 screens there and also topped the weekend box office in Malaysia. It also has set new records in Singapore grossing over $201,408.
Kaththi became the highest grossing Tamil film of 2014 in US. In the UK box office it grossed £319,310 in 12 days. In Australia, Kaththi collected $160,890 and has surpassed the opening weekend collection of Kochadaiyaan ($119,597) and Anjaan ($107,013) for 2014. The film had a lifetime business of over A$194,341 in Australia and became the highest grossing Tamil film of the year there. The film made approximately $1.86 million in Malaysia and has emerged as the third highest Tamil grosser. The grossed an estimated ₹124 crore (US$19 million) worldwide, making it one of the highest grossing Tamil films of all time.
Kaththi was remade in Telugu as Khaidi No. 150 (2017), directed by V. V. Vinayak and starring Chiranjeevi.
Kaththi is also scheduled to be remade in Hindi as Ikka (2018). The film will be directed by AR Murugadoss, and Akshay Kumar in lead.