‘Ashtadhyayee’ was written by

The Ashtadhyayi is one of the earliest and most systematic treatises on Sanskrit grammar. Composed entirely of nearly 4,000 extremely concise aphoristic rules called sutras and organised into eight chapters (hence 'Ashta-adhyayi', meaning 'eight chapters'), it codifies the phonology, word-formation, and syntax of Vedic and classical Sanskrit, and remains the foundational text of Sanskrit linguistics.

This treatise was composed by Panini, an ancient Sanskrit grammarian believed to have lived around the 4th century BCE near Shalatula (in present-day Pakistan). His systematic grammatical framework is still studied by linguists worldwide, and it later drew detailed commentaries from scholars such as Katyayana and Patanjali.

Why the other names do not fit:

• Shukadeva: remembered as the narrator of the Bhagavata Purana to King Parikshit — a work of devotional narrative literature, not a grammatical treatise.

• Valmiki: the sage-poet credited with composing the epic Ramayana — a narrative poem, an entirely different genre from a grammar text.

• Vedvyas (Ved Vyasa): traditionally credited with compiling the four Vedas and composing the Mahabharata and the Puranas — works of scripture and epic narrative, not grammar.

Hence, the author of the Ashtadhyayi is Panini.