Arnuwanda I was a king of the Hittite empire. He became a ruler by marriage and was very religious.
Arnuwanda became a king by marriage. His wife was Ašmu-nikal, daughter of king Tudhaliya I. He became a successor of Tudhaliya as his son-in-law. He began his reign under a co-regency with Tudhaliya. His campaigns include an unsuccessful expedition against the kingdom of Arawa.
Arnuwanda's parents are not known. He was a son-in-law of Tudhaliya and Nikal-mati. He had two sons, prince Ašmi-Šarruma and king Tudhaliya II. There is a very fragmentary text in which Arnuwanda names his son Tudhaliya as his future successor.