Emergency services were called to Cann Bridge Street following reports a man had gone into the river at around 9.15am today (Monday, January 24).
Five fire engines and a boat from Lancashire Fire and Rescue Service attended the scene, as well as police, a helimed crew and paramedics.
The man was pulled from the water by members of the public before being taken to hospital by ambulance in "serious condition".
Police later confirmed the man was "pronounced dead a short time later despite the best efforts of medical staff".
"Enquiries into the incident are ongoing," a spokesman for Lancashire Police added.
The man has not yet been identified.
A spokesman for Lancashire Fire and Rescue Service said: "Firefighters assisted with moving the person and helped them to an ambulance, where they were conveyed to hospital.
"Crews used rope and water rescue equipment and remained on scene for approximately two hours."
Anyone with information can contact police on 101, quoting log number 0306 of January 24.
Thanks for reading. If you value what we do and are able to support us, a digital subscription is just £1 per month for the first two months. Try us today by clicking HERE.