Irish Ferries, a subsidiary of Irish Continental Group plc (ICG), is launching a new service on the Dover - Calais route.
The Port of Dover has welcomed the move and says it is a clear signal of market confidence in Dover.
The operators say it will strengthen the "landbridge" between the UK and Europe and will improve reliability for importers and exporters.
"We are very excited about launching our services on the best short sea ferry market in the world and we believe we can bring more choice for customers in the years ahead," said a spokesperson for Irish Ferries.
"This additional capacity on the Dover - Calais route will significantly strengthen the capacity and reliability of the landbridge for exporters and importers. Hauliers will now have one operator providing an inclusive service on the Dublin - Holyhead, Rosslare - Pembroke and Dover - Calais routes. This will allow exporters and importers easier, cheaper, and quicker access to our European markets via the Common Transit Convention."
The ferries will also carry passengers but the company says that will depend on the easing of Covid-19 travel restrictions.
Doug Bannister, Chief Executive, Port of Dover, said: "We are delighted to welcome Irish Ferries to Dover. This announcement gives the millions of customers across the UK and the Republic of Ireland who value the intrinsic benefits of the shortest sea crossing to Europe, the prospect of even more choice. We believe the inclusive landbridge product will be popular with Irish exporters and will strengthen the just in time supply chain into the European Union.
"This is a clear signal of market confidence in the Dover route and will complement the resilient services currently provided. We wish Irish Ferries every success and look forward to having them on the route in the summer and working together as part of the Dover team building the future success of the Short Straits."
Jean-Marc Puissesseau, Chairman, Port of Calais, said: "The commencement of the service operated by Irish Ferries emphasises the strategic position of the port of Calais in the trade between Ireland, the United Kingdom and the continent. It is a clear sign of confidence just a few weeks before the opening of the new port of Calais".
The Isle of Inishmore is said to be one of Europe's largest, well-equipped and most modern car ferries. It has a Club Class lounge and a play area for children. It can carry 2,200 passengers, 800 cars and 150 lorries.