The word Maithili is derived from the word Mithila that was an ancient kingdom of King Janaka. Maithili was considered as the language of the common folk. The earliest work in Maithili language was the Varna Ratnakar by Jyotirishwar Thakur dated about 1324. Jyotirisvara Thakur composed Varnaratnakara in pure Maithili language. It is considered as the earliest prose in any Indian language. The various dialects of Maithili are standard Maithili, southern standard Maithili, eastern Maithili, Western Maithili, Jolaha and Central Colloquial Maithili.
Vidyapati Thakur(1360 to 1450) was an epoch making poet who came up under the patronage of the like-minded king Shiva Simha and his queen Lakhi Ma Devi. He produced several immortal songs in Maithili language. They were based on the theme of Radha and Lord Krishnaand the domestic life of Lord Shiva and Parvati. After the invasion of Mithila by the Sultan of Johnpur, Delhi, Onibar rule became weak and the literary activity shifted to Nepal.
The earliest reference to Maithili is in Amaduzzi's preface to Beligatti's Alphabetum Brammhanicum that was published in 1771. Maithili is considered as a distinct dialect. When Mahesh Thakur, a great pandit of the Khandvala family of Maithil Brahman was installed as a feudal chief of Mithila under the Mughal Empire, literary activity in Mithila language gained momentum in dance, drama and music. After a gap of about two centuries, Umapati Upadhyaya wrote parijataharana in Maithili.
Many devotional songs were written by Vaishnava saints, included Govendadas in the mid-17th century. Ragatarangni of Lochana wrote a significant treatise on the science of music, describing the ragas, talas prevalent in Mithila. After death of Maheshvar Singh, the ruler of Darbhanga Raj, in 1860 it was taken over by the British Government as trustee.
Publication of compositions like Maithil Hita Sadhana (1905), Mithila Moda (1906), and Mithila Mihir (1908) encouraged writers. Maithil Mahasabha, the first social organization was established in 1910 for the development of Mithili and Maithili languages. Maithil Mahasabha had also campaigned for official recognition of Maithili as a regional language.
In 1965, Maithili language was officially accepted by Sahitya Academy. In 2003 it was recognized in the VIII schedule of the Indian Constitution as a major Indian language.