Michael Rayappan is a rowdy working for public welfare in a Chennai slum. His friend Kathir, the coach of the Tamil Nadu women's football team, gets attacked by goons while driving home. Michael fights them off but realises his archenemy Daniel has stabbed Kathir, leading to spinal injuries that prevent him from accompanying the team. The team blames Michael for his condition, while Kathir tells a member of the federation to replace him with a former footballer named "Bigil" who is none other than Michael.
The scene shifts to seven years back, Michael is a talented footballer who brings glory to the state and his slum by winning matches. His father Rayappan, a don, gets into a brawl with the henchmen of Alex, Daniel's father. This leads to bitter relations between the three. Rayappan encourages Michael to become a champion and stay away from the life of violence. When Michael and his team are not selected for the Indian football team, Rayappan personally convinces the All India Football Federation president, J. K. Sharma, to get the boys selected. However, while leaving, Michael witnesses Rayappan getting stabbed to death by Alex and his henchmen, following which he jumps off the train and proceeds to kill the goons including Alex. Following Rayappan's death, Michael decides to stay in the slum and leaves behind his dream. Michael accepts Kathir's request to return to footballing. He accompanies the team to Delhi as their coach, along with his girlfriend Angel who becomes the team's physiotherapist. Michael is later attacked in the premises by some goons, due to which he is nearly expelled but J. K. Sharma comes to his rescue. The girls, reluctant to co-operate with Michael due to his violent background, also blame him when they lose to Manipur in the opening match. A dejected Michael tenders resignation to Sharma, but soon learns that Sharma was behind the attack on him and was trying to seek revenge. It is then revealed that Sharma did not object to Bigil based on his father's criminal background, but because he wanted a bribe, and that Rayappan had later tortured and blackmailed him to select Michael and his team. Michael now starts training his team, eventually making them toil and realise the spirit of teamwork. He and Angel also succeed in reviving former key players to boost the team's strength: Gayathri, a Brahmin girl who had to give up football after marriage in a conservative family; and Anitha, who has gone into depression after an acid attack. On the day of their match with Haryana, Sharma gets Michael arrested due to the brawl in the premises. With the help of his own men, Michael frees himself and rushes to the stadium where he finds some Haryana players and the referee manipulated by Sharma using dirty tactics. Michael instructs a player Pandiyamma to hit the referee in an accident, following which they beat Haryana and win all the remaining matches. They qualify for the finals at Chennai where they are to play with Manipur again. Michael's team succeeds in winning the match through a penalty shootout. Seated in a wheelchair, Kathir watches Michael and the team dedicate their success to him.
During the credits, Sharma gets arrested in Malaysia after he is framed by Michael for drug possession. Michael quits rowdyism and takes up football coaching for children, following which Daniel asks him to train his son who now aspires to become like "Bigil".
