The 50-year-old actor made the revelation during a late night chat show when discussing his recent discovery that his family owned the majority of Dublin in the ninth century, reported Sun online.
"I found out my ancestors were the rulers of north Ireland," he said.
Cruise was in town to promote his new sci-fi flick 'Oblivion'.
During his stay he was presented with a certificate of Irish heritage by the Minister of Foreign Affairs and Trade Eamon Gilmore after two female fans researched his family lineage as a gift.
Hollywood is a village in west County Wicklow.