The silverback gorilla was 29-years-old and fathered six children during his time in the zoo.
Dublin Zoo say they’re waiting on a post-mortem to find out the reason he died.
Staff have said he was a very gentle and calm gorilla, and will be greatly missed.
"Harry was a very gentle and calm gorilla and he will be greatly missed by everyone at Dublin Zoo."
The news comes days after a gorilla was shot at Cincinnati Zoo after a four-year-old fell into the enclosure.