The MV Glen Sannox is to be deployed to help passengers heading for a music festival later this month.
The £200m CalMac ferry will provide additional capacity on the Ullapool to Stornoway route for those heading for HebCelt from 15-18 July.
It is hoped the vessel, which will join MV Loch Seaforth on the crossing, can provide transport for up to 10,000 extra passengers over the weekend.
The ferry will be temporarily renamed the “HebCelt Special” when it begins crossings on Monday.
Glen Sannox can carry an additional 852 passengers, 127 cars or 16 HGVs, added to the Loch Seaforth capacity of 700 passengers, 143 cars or 20 commercial vehicles.
Both vessels will make twice daily crossings until Saturday.