Old Persian is an ancient Iranian language that was spoken during the Achaemenid Empire, which lasted from the 6th to the 4th century BCE. It is primarily known from inscriptions, such as those of Darius the Great and Xerxes I, and is written in a cuneiform script. As a member of the Indo-Iranian branch of the Indo-European language family, Old Persian is significant for understanding the history and culture of ancient Persia. It eventually evolved into Middle Persian, which was used during the Sassanian Empire, and laid the groundwork for modern Persian.