Vyasa
Vyasa (Sanskrit: व्यास, vyāsa, literally “Compiler”) is a central and revered figure in most Hindu traditions. He is also sometimes called Veda Vyāsa (वेदव्यास, veda-vyāsa, "the one who classified the Vedas") or Krishna Dvaipāyana (referring to his complexion and birthplace). He is the author of the Mahabharata, as well as a character in it. He is considered to be the scribe of both the Vedas and Puranas. Vyasa is also considered to be one of the seven Chiranjivins (long lived, or immortals), who are still in existence according to Hindu belief.
According to the Vishnu Purana, "Veda Vyasa" is a title applied to the compilers of the Vedas who are avatars of Vishnu; 28 people with this title have appeared so far.
The festival of Guru Purnima is dedicated to him. It is also known as Vyasa Purnima, for it is the day believed to be both his birthday and the day he divided the Vedas.
In the Mahabharata
Vyasa appears for the first time as the compiler of, and an important character in, the Mahabharata. It is said that he was the expansion of the god Vishnu who came in Dwaparayuga to make all the Vedic knowledge available in written form which was available in spoken form at that time. He was the son of Satyavati, daughter of the fisherman Dusharaj, and the wandering sage Parashara (who is credited with being the author of the first Purana: Vishnu Purana). He was born on an island in the river Yamuna. There are two different views regarding his birthplace. One of the views suggests that he was born in the Tanahun district in western Nepal, other view suggests that he was born on Island in Yamuna river near Kalpi, Uttar Pradesh, India. Vyasa was dark-complexioned and hence may be called by the name Krishna, and also the name Dwaipayana, meaning 'island-born'.