The 3,000–gt St Helen (built 1983) served the route between the Isle of Wight and Portsmouth for 30 years, the BBC reported.
It has been linked to Delcomar for a run to Sardinia. The Italian company already operates a former Wightlink sistership.
Captain Peter Hayes said St Helen had been the "flagship of the fleet".
"She's been so reliable and provided such a good service over these past 32 years, we'll be sorry to see her retire and move to warmer climates," he added.
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