Hurricane Dennis was an early-forming major hurricane in the Caribbean and Gulf of Mexico during the record-breaking 2005 Atlantic hurricane season. Dennis was the fourth named storm, second hurricane, and first major hurricane of the season. Forming in July, the hurricane became the strongest Atlantic hurricane ever to form before August at the time, a title it held for only six days before being surpassed by Hurricane Emily.

Dennis made landfall in Cuba twice as a Category 4 hurricane on the Saffir–Simpson scale and made landfall on the United States' Florida Panhandle as a Category 3 storm, coming less than a year after the devastating Hurricane Ivan. Dennis killed 88 people in total and was responsible for $2.5 billion (2005 USD) in damages to the United States, not counting additional damage in the Caribbean.