Tanhaji (Ajay Devgn) is an action epic about the titular Maratha warrior and Shivaji's military commander who lost his father in a battle (when he lost his life defending his village from Muslim invaders in 1647 AD much before the arrival of the Brits) and grew up to become a fierce warrior with powerful combat skills. Tanhaji was Shivaji's favorite commander. In 1664 Marathas were able to keep the Mughals in Delhi from conquering the whole of India. Mughal emperor Aurangzeb dispatches his commander Mirza Raje Jai Singh (Yuri Singh) (a Hindu) with an army of 80,000 warriors to quell the Maratha challenge. Mirza Raje surrounds all Maratha forts including Kondhana. with no other option to rescue the fort, Shivaji gifts the Kondhana fort to Aurangzeb as a peace offeringWhen Mughal emperor Aurangzeb (Luke Kenny) recruits his trusted guard Udaybhan Singh Rathore (Saif Ali Khan) to take control of the Kondhana Fort (along with the world's largest cannon at the time), Shivaji (Sharad Kelkar) decides not to engage Tanhaji whose son is going to get married soon. But stopping Udaybhan is critical as if the cannon reaches Kondhana, South India will not be safe from Mughal rule. Savitribai Malusare (Kajol) is Tanhaji's wife. As Tanhaji learns of Udaybhan's heading towards the fortress, he decides to take charge and stop the rival army from reaching their destination. He personally tells Shivaji that he will postpone his son's wedding till the Uday issue is sorted. Tanhaji figures out the route to be taken by Uday to reach Kondhana, and lays in siege.This doesn't turn out to be easy as Udaybhan finds himself helped by people who don't want Tanhaji to succeed, resulting in battles and attacks that ensue as the plot unfolds. Chandraji Pisal (Ajinkya Deo) is another commander of Shivaji, who betrays him as he is jealous of Shivaji always favoring Tanhaji. Chandraji sends information to Uday of Tanhaji's position and the town where he intends to commence his attack on Uday's forces.To foil Tanhaji, Uday captures Maratha, disguises them as Mughals and send them through the mountain pass where Tanha's forces are waiting. Tanhaji attacks and realizes late that he is attacking Marathas. Meanwhile Uday transports the cannon through barges on a water route and reaches Kondhana. Tanhaji realizes that he has been betrayed. He travels to Kondhaba and makes patriotic overtures to the palace guards, who agree to side with Tanhaji against UdayBhan. The palace guards smuggle Tanhaji inside the fort, but he is arrested by Udaybhan's personal guards who torture him. Tanhaji manages to escape with the help of some Rajputana sympathizers who no longer want to support Mughals in conquering India.Tanhaji recoups at his native village. He gathers his strength and army and attacks Kondhana via secret tunnels in the fort that only a few insiders knew about. Gate by gate Tanhaji's elite force ekes out little victories. Udaybhan is rattled and orders the cannon to open fire on Shivaji's fort. Tanhaji gives his own life but stops Udaybhan's cannon from firing and kills Udaybhan while destroying the cannon. The Mughals never conquer the South of India.