The Mahabharata has around 100,000 verses, making it the longest epic poem ever written. Similar to the Ramayana, the Mahabharata is also an ancient Indian Sanskrit epic, giving the chronicle of a royal family having two branches Kaurava and Pandavas, who, in the Kurukshetra War (Mahabharata war), the battle for the throne of Hastinapura. In this war, Lord Krishna sided with Pandavas while his army was asked to support Kauravas. Lord Krishna imparted wisdom to Arjuna before the start of the war and that is Bhagavad Gita.
If the Ramayana is the story of the royals giving away their rights then the Mahabharata is the story of a great war for rights.