The Red Ensign was ceremonially raised at Sunderland Civic Centre by the Mayor, Councillor David Snowdon and at Port of Sunderland by Captain Kevin Markwell.
The Mayor was joined by guests including the Deputy Lieutenant for Tyne of Wear, Mr Norman Taylor, MBE, DL and Captain Stephen Healy from national maritime welfare charity, Trinity House, members of the public, and former and serving merchant seamen to show their support.
A welcome speech from the Mayor was followed by the Deputy Lieutenant reading out a message from HRH The Earl of Wessex, who is the President of Seafarers UK which raises funds to help seafarers and their families in need.
Captain Healy of Trinity House then told those assembled more about the Merchant Navy, and the service and sacrifice of all those who have sailed under the Red Ensign, and called for a minute's silence before the ceremonial raising of the flag in their honour.
Sunderland City Council supported the event organised by national charity Seafarers UK, to help raise public awareness of the Merchant Navy's massive contribution to the life of the 'island nation' of Great Britain.
As a major shipbuilding centre, Sunderland provided both materials and seafarers for the merchant fleet during both the First and Second world wars.
Merchant Navy Day was first held in 2000, with the 'Fly the Red Ensign' campaign launched in 2015 to remind people of its national significance and encourage their support.
The Mayor of Sunderland, Cllr Snowdon said: "Our city has a very proud naval tradition and maritime heritage, and many people from our community have served in the Merchant Marine.
"As Mayor I was honoured and proud to represent the people of Sunderland at this annual event, and raise the famous Red Ensign on their behalf in tribute and appreciation of the contribution made by the Merchant Navy to all our lives.
"I hope people were encouraged to pay their own personal tributes to the Merchant Navy, by seeing the Red Ensign flying proudly at the Civic Centre."
Sunderland is one of many local authorities across the country invited to raise the flag in support of Merchant Navy Day, and this will be the fifth consecutive year the Red Ensign has been raised outside the Civic Centre in commemorative celebration of the event.
Chair of the Sunderland Armed Forces Partnership, which is led by Sunderland City Council and works with veteran's groups and serving personnel and their families, Jessica May added: "As an 'island nation' we owe a huge debt of gratitude to the Merchant Navy who kept Britain afloat during two World Wars, and continue to rely on them today for the UK imports vital to our economic survival.
"Very often the bravery of those who serve or have served in the Merchant Navy can go unrecognised, despite their massive impact on all our lives and on world history.
"Merchant Navy Day is our opportunity to redress that balance, and raise the Red Ensign in tribute."