Valmiki (/vɑːlˈmiːki/; Vālmīki) is celebrated as the harbinger-poet in Sanskrit literature. He lived in the first millennium BCE. He is the author of the epic Rāmāyaṇa, based on the attribution in the text of the epic itself. He is revered as the Ādi Kavi, which translates to First Poet, for he invented śloka (i.e. first verse or epic metre), which set the base and defined the form to Sanskrit poetry.
Example via www.ramdass.org: “The Mahabharata” and “The Ramayana”