Christopher and Sharon Bell, from Killingbeck in Leeds, were among the 38 people killed at a hotel beach resort in Sousse on June 26 four years ago.
Today, in Birmingham's Cannon Hill Park, the Duke of Sussex attended a moving ceremony alongside around 200 family and friends of those who died.
The memorial will also act as a focus of remembrance for those killed in a separate attack on the country’s famous Bardo Museum on March 18, 2015. There, one British woman, Sally Adey, a 57-year-old solicitor from Caynton near Shifnal, Shropshire, was among 22 killed.
At Sousse, 30 British tourists staying at the Hotel Rui Imperial Marhaba complex in Port el Kantaoui were among 38 killed, with dozens more injured.
Mr Bell, 59, and his wife, 54, were described at an inquest as a loving couple who doted on their two grandchildren. They had two sons and a daughter.
They were both shot dead close to the hotel swimming pool.
Speaking at the service today, Prince Harry said: "In memory of all those who lost their lives.
"And to the families whose lives were changed forever by these events.
"I would like to pay my deepest respects to you and officially dedicated this memorial to your loved ones."
Holding a single white rose, he then turned and walked to the memorial's centre-piece, where he laid the flower.
The Sousse terrorist attack was the deadliest on British citizens since the July 7/7 London bombings in 2005.
Islamic State claimed at the time that it was behind the attack by Tunisian student Seifeddine Rezgui.
Last month, seven people were jailed over the two attacks.
Among those killed at Sousse were three members of the same family; Charles Patrick Evans, 78; his son Adrian Evans, 49, and grandson Joel Richards, 19.
Joel's brother Owen Richards, then 16, survived and was later praised for his bravery at the scene by a coroner at inquests into the deaths.
After the attacks, he and his mother Suzanne Richards set up the Smile for Joel Charity, providing support for other victims of terrorism.
Speaking after the ceremony, Mrs Richards said: "We're looking forward to seeing the memorial being officially unveiled. We had a sneaky peak yesterday and it was beautiful.
"It's lovely to think people can actually come and see all the names of those killed and reflect on what happened.
"It is very difficult and also today is my Dad's (Charles') birthday."
Owen Richards, now 19 and studying at university, said: "Its really important not just for the families but also generally for the wider public to take an interest and be able to remember what happened, and not forget it.
"Because there were things that should have been learned from that day and by remembering it hopefully those lessons (will be learned) and it will stop it happening again."
The park site was selected in consultation with the families due to its central location, its "seclusion and tranquillity" and as "being a place of public prominence", the Foreign and Commonwealth Office (FCO) said previously.
The centre piece of the memorial, designed by George King Architects, is a sculpture titled 'Infinite Wave' made up of 31 individual stainless steel rods, each representing the Britons who lost their lives.
From the side, the memorial also takes the shape of a dove of peace taking flight, while concentric rings of stone and turf ripple outwards.