Who is Shakuntala?

Devi Shakuntala was a very beautiful daughter of Brahmarishi Vishwamitra and Apsara Menaka. Menaka was on a mission to make Vishwamitra away from his penances as he was becoming too strong for Indra to handle. Once they had a baby, Vishwamitra realised her real purpose and the futility of his love for her and he left Menaka. Menaka too left the baby near Himalayas and left for heaven. The poor baby was left to die in nature but birds (Shakunt) gathered around the baby to save her from vagaries of nature. Rishi Kanva found her and adopted the baby as his own daughter and named her Shakuntala (protected by birds).

When once King Dushyant of Hastinapur came to the hermitage while he was on a hunting spree, he saw beautiful Shakuntala and enquired about her. He was shocked that celibate Kanva had a daughter. She introduced herself and he proposed her. She denied saying her father was not at home. He convinced her to do Gandharva Vivah with his sweet words and they consummated. He left her saying he would return soon. She told about her marriage to Kanva who did not get angry.

She gave birth to a son who was very brave and played with wild beasts effortlessly. She named him Sarvadaman. She was waiting and waiting but Dushyant didn't come to take her. She lost her patience and went to Hastinapur with her 12 year old son.

When she told Dushyant to take her and her son in the palace, he brutally insulted her and her lineage and even called her mother Bandhaki (the same bad word Karna used for Draupadi). Shakuntala was hurt and lost her patience with the betrayal and she too abused Dushyant. As she was about to go a celestial voice revealed that she was his wife and he should take her. Then Dushyant said they were his family and he didn't take her the first time as he didn't want his courtiers and people to think he just took any random woman as his wife. He asked forgiveness from Shakuntala for his hurtful words and also forgave her for her words even though she didn't say sorry and rightly so. He took them to his mother and told her Shakuntala was his daughter in law and the boy was his son. The Queen Mother accepted them with happy tears. Sarvadaman later became famous King Bharat.

Source- Mahabharata

In Mahabharata, Who was Shakuntala? What was her role in this great epic?

Shakuntala

Shakuntala was daughter of Vishwamitra (son of Gadhi) amd Apsara Menaka (a celestial court maiden of Indra). Menaka had a mission to stray away Vishwamitra from his penance and when she succeeded, she left her baby on Himalayas and went to Heaven. The baby was saved from wild beasts by birds and Rishi Kanva found her and took her to his ashram and made her his adoptive daughter.

Once King Dushyant, son of Ilil and Rathantarya once came to Rishi Kanva’s ashram when he was on a hunting vacation, he saw beautiful Shakuntala and instantly fell in love. He proposed her but she denied saying that her father was not at home. He said she should do Gandharva Vivah with him as it's acceptable for warrior clan. After much convincing they got married and also consummated the marriage. He left promising he would come to take her back. When Rishi Kanva was told about this, he wasn't angry. Shakuntala patiently waited and gave birth to her son who was named Sarvadaman because he was very brave and often used to play with wild beasts and ride them.

Shakuntala became impatient when he didn't come back to take her and Sarvadaman was already twelve now. She went to his palace and asked him to accept their son.

Dushyant despite remembering her insulted her purposely and said many bad things about her and her family and called her a liar for trying to make her son as a Prince by lying. Such behaviour shocked Shakuntala and she became angry, she tried to convince him by saying he should atleast accept the son but he was repeatedly insulting her. Then Shakuntala said unpleasant words to him and as soon as she was about to walk out, a celestial announcement happened telling Dushyant to accept his family.

Then Dushyant declared that she was his wife and Sarvadaman was his son and he declared if he hadn't done this whole facade then his people and court would doubt her and their son. They would think he accepted them out of lust and pity and not genuine love. He asked forgiveness for his harsh words and also told her that he forgave her for her harsh words. Later, he took his family to the palace and introduced them to his mother.

Sarvadaman was appointed Crown Prince and he became famous with the name of Bharat and he subdued every king in the subcontinent.

Source- Mahabharata

Kalidas' work Abhigyan Shakuntalam is a modified, more romantic work of the original story.