Hattusili I (?attu?ili I) was a king of the Hittite Old Kingdom. He reigned ca. 1650-1620 BCE as per middle chronology, the most accepted chronology nowadays, or alternatively ca. 1586-1556 BCE (short chronology). Recent excavations in Zincirli Höyük, Southern Turkey, suggest that Hattusili I destroyed a complex at that site in the mid to late 17th century BCE, which can confirm the middle chronology dating for his reign. This event could have been part of his campaign against Zalpa in order to disrupt an exchange network connected to Aleppo that previously linked the Euphrates, North Syria, and Central Anatolia.
He used the title of Labarna at the beginning of his reign. It is uncertain whether he is the second king so identified, making him Labarna II, or whether he is identical to Labarna I, who is treated as his predecessor in Hittite chronologies.
He is the earliest Hittite ruler for whom contemporary records have been found. In addition to "King of ?attu?a", he took the title "Man of Kuara", a reference to the prehistoric capital and home of the Hittites, before they had occupied Ne?a.
A cuneiform tablet found in 1957 written in both the Hittite and the Akkadian language provides details of six years of his reign. In it, he claims to have extended the Hittite domain to the sea, and in the second year, to have subdued Alalakh and other cities in Syria. In the third year, he campaigned against Arzawa in western Anatolia, then returned to Syria to spend the next three years retaking his former conquests from the Hurrians, who had occupied them in his absence.
The end of his reign is of historical importance because of his Succession Proclamation. This document, written in first person, tells of ?attu?ili coming back wounded from his last military campaign. On his deathbed he is enraged by the attitude of his heir and how he is conspiring with his mother and cousins. ?attu?ili then explains that for these reasons Mursili, his grandson, will be the next king instead, and urges the army and public servants to obey him.
This apparently worked since Mursili indeed became king and continued ?attu?ili's military campaigns, finally conquering Alepo and sacking Babylon.