Irish Continental Group hare agreed a deal to sell its "Oscar Wilde" cruise ferry to MSC Mediterranean Shipping Company for €28.9m.
The money will be paid in instalments over six years, up to 2025.
The Oscar Wilde, built in 1987, was acquired by ICG in 2007 and was operated by its subsidiary Irish Ferries on the Ireland-France route.
ICG said the proceeds of the sale, less the net book value of the Oscar Wilde at €7.7m and related disposal costs, will result in a profit for the company.
It said this will be reported as part of the 2019 financial results of ICG.