The total of 15,299 cases in the hard-hit southeastern state was up sharply, 47 percent above the previous day’s total, the Florida state health department reported.
The state also recorded a one-day toll of 45 deaths attributed to COVID-19.
Over five days, Florida has tallied 55,842 new cases.
The previous one-day record for new cases had been held by California, with 11,694 cases registered on Wednesday, and before that by New York, with 11,571 cases reported on April 14.
Florida’s Republican governor, Ron DeSantis, moved quickly to begin unwinding the state’s lockdown starting May 4, before most other states.
In an unusually direct criticism, top US health official Anthony Fauci said Thursday that Florida had moved out of its lockdown before public-health indicators justified such a move.
DeSantis contested that, saying his decision was based on the best data at the time.
In late June, in a partial reversal, DeSantis ordered bars to be re-closed in an effort to curb the spread of the disease, but infection numbers continued to rise.
But the Florida governor has refused to require mask-wearing in public — a step some other southern governors have now taken — saying that was a matter for local officials to decide.