She is in Cardiff to officially open the Sixth Senedd along with the Prince of Wales and Duchess of Cornwall.
The opening of the Welsh Parliament had been delayed due to the pandemic, and would usually have been held shortly after the election in May.
First minister Mark Drakeford has welcomed the visit, claiming the presence of the Queen highlights the “significance of the Parliament” in Wales.
Speaking to Sky News, Mr Drakeford said: “Decisions are made in four different parliaments and I know the Queen has always taken very seriously the job that she does in marking that.
“As I say, she’s never missed an opening of a new Senedd term and despite the circumstances, and her age, she will be making that effort again today.”
During the opening of the Senedd, the Queen will make a speech in the chamber, as will the first minister and Elin Jones MS, Llywydd of the Senedd.
The Queen attended a similar event for the opening of the Scottish Parliament last month.
During the opening, The Queen has urged Scotland’s MSPs to “help create a better, healthier future” by tackling the challenges of climate change ahead of the Cop26 conference.
She also reflected on the “deep and abiding affection” and happy memories she and the late Duke of Edinburgh shared of Scotland as she formally opened the new session of the Scottish Parliament.
The Queen said: “The beginning of a new session is a time for renewal and fresh thinking, providing an opportunity to look to the future and our future generations.
“Next month, I will be attending Cop26 events in Glasgow.
“The eyes of the world will be on the United Kingdom – and Scotland in particular – as leaders come together to address the challenges of climate change.
“There is a key role for the Scottish Parliament, as with all parliaments, to help create a better, healthier future for us all, and to engage with the people they represent – especially our young people.”