The Senedd was recalled on Sunday, a day before it was due to return from Summer recess, to carry out a motion of condolence in honour of the former monarch who died on Thursday.
Politicians gathered at the Senedd building in Cardiff Bay from 3pm, hours after Charles was proclaimed King to the people of Wales at a ceremony in Cardiff Castle.
The Queen’s coffin was being driven in a cortege from Balmoral to Edinburgh as members spoke.
Beginning the session, the Senedd’s speaker Elin Jones said the motion would be presented to King Charles during his visit to Wales on Friday.
Ms Jones said: “As in all parliaments, our views represent the diversity of views of the people we serve.
“And although our views may differ on the institution of monarchy itself, they will differ little on the way Elizabeth II executed her role as monarch over a lifetime of public service, how her wisdom and dedication to office was valued, and how we mourn her sad loss and hold her family in our thoughts.
“Elizabeth II looked for what united rather than what created division.
“We too can seek that unity today in our condolence.”
The Queen, who took to the throne 47 years before Senedd was created, visited its yearly opening ceremony six times over the past 23 years.
Her final visit was 11 months ago in October 2021.
First Minister of Wales Mark Drakeford said: “We know that it was the Queen’s own personal decision back in 1999 to come to Cardiff to open the first term of the assembly.
“She did that ignoring the advice provided to her.
“She returned here for the final time over 20 years later, in accordance with that personal commitment to Wales and its democratic institutions.”
He continued: “In a remarkable life, the last 24 hours of the Queen’s reign were amongst the most extraordinary.
“No-one who watched it unfolding will forget the sight of someone so determined to fulfil her constitutional obligation – confirming a new Prime Minister – something which only she could undertake, despite the unavoidable impact on her reserves of strength.
“Nothing more could have clearly expressed the overriding sense of duty which was amongst her greatest characteristics.”
Welsh Conservative leader Andrew RT Davies said: “There was never a quibble, there was never a qualm, there was never a moan.
“It was always in public service and duty that Her Majesty put herself first for the country and the Commonwealth.”
Mr Davies praised the Queen for her ability to put those she met at ease and to focus on the individual, saying she was a monarch who “stayed relevant right the way through the ages”.
Plaid Cymru’s Adam Price said that despite her “fairy tale existence” she managed to foster a “mutual connection, almost a personal relationship” with countless millions.
“It’s the Queen herself that best captured this sense of affinity in the words she used about Princess Diana in the days after her tragically untimely death.
“‘No-one who knew her will ever forget her. Millions of others who never met her, but felt they knew her, will remember her’.
“They are words that ring true now for Queen Elizabeth, as they did then for Diana,” he said.
Mr Price said the Queen was known to “confound” people who saw her as a one-dimensional character, referencing moments throughout her reign including when she bowed her head at the garden of remembrance in Dublin during her first visit to the Irish Republic.
“For some, this will be a moment of great anxiety,” he added.
“But perhaps, as Queen Elizabeth begins her final journey and we consider what the future holds, we can follow the Queen’s own injunction in that great Dublin speech to bow to the past, but not be bound by it.”
Welsh Liberal Democrats leader Jane Dodds said that as the world changed, the Queen was “ever present”, and called her a “friend to Wales”.
Recalling an anecdote from when she met the Queen last October, Ms Dodds said: “I was introduced as the member representing Mid and West Wales, a large area of Wales, and I think I said something like ‘we have more sheep than people in the area I represent’.
“Her sharp and quick response to me was, ‘Well, how do you know what their views are?'”
Reflecting on a more sombre moment in Wales’ history when a colliery spoil tip collapsed on a school in Aberfan, killing 28 adults and 116 children, Ms Dodds said: “Many will remember Elizabeth II’s visit to Aberfan in 1966 and recall her sharing in the grief felt by the people.
“As someone recounted after the disaster, ‘It felt like she was with us from the beginning’.”
All other business in the Senedd has been suspended until after the state funeral on September 19.