Two guards received the new colours in the Quadrangle at Windsor Castle
The Queen has presented new colours to the 1st Battalion Irish Guards in recognition of their service in Iraq.
Family and friends watched as the Queen addressed more than 500 soldiers as the battalion's Colonel-in-Chief at a ceremony at Windsor Castle.
The soldiers, based at the town's Victoria Barracks, had achieved "a remarkable record of service" she said.
The colours display the regiment's "Iraq 2003" battle honours for the first time.
They were the first regiment to go into Basra during the war and have lost four soldiers since 2003.
They last returned from operations in Iraq in December 2007.
About 1,000 invited guests, mostly families and friends of the soldiers, watched as the Queen walked the length of the Quadrangle at Windsor Castle to inspect the parade.
Two soldiers, Lt Adam Kennard and 2nd Lt Charlie Gair, were then presented with the battalion's new colours.
Commending the regiment's engagement in "the most testing operations", the Queen also recognised its service in Kosovo in 1999.
"You have the greatest cause to be proud of your achievements," she said.
The Queen, accompanied by the Duke of Edinburgh wearing a guard's uniform, also recognised others currently deployed in southern Afghanistan and those who had suffered losses.
"This has been a remarkable record of service, but not without cost.
The Queen and duke inspected the guards in front of 1,000 guests
"In Iraq, four members of the regiment were killed, others among you have been wounded and otherwise endured great suffering.
"We should commend your families too for the loyal support they have given amid the uncertainties of your often long and difficult absences."
She added: "One thing is certain. The men who rally round these colours will continue to uphold the steadfast values of comradeship and selfless sacrifice for which the regiment has stood throughout its history."
The last presentation of colours to the 1st Battalion Irish Guards took place in 1997.
The old colours were earlier paraded up to Windsor Castle before being marched before the battalion, and then away to Auld Lang Syne to symbolise their retirement from service.