Horrified onlookers witnessed a man plunging from Carlisle Bridge.
Police were called at 4.30pm on Sunday after the man, a 64-year-old from Morecambe, fell from the bridge at Lancaster.
Ambulance crews and the police found him unconscious with multiple injuries.
The man was flown by air ambulance to the Royal Preston Hospital where he died of his injuries at 5.40pm.
His death is not being treated as suspicious.