Queen Elizabeth II awarded Keith Palmer with the prestigious George Medal, which is presented to someone who has been responsible in saving lives.
"His actions provided time for other officers to react and shoot and stop the assailant. Palmer's bravery and professionalism unquestionably saved lives. Palmer did his duty. In doing so he made the ultimate sacrifice," the police constable's citation reads.
The 38-year-old was on guard at the main gates of the Palace of Westminster, which houses the UK Parliament, on March 22 when Khalid Masood rammed a car into the side of the building before getting out and trying to gain entry into the House of Commons complex.
His award on the Civilian Gallantry List as part of the Queen's annual Birthday Honours list released today is for "confronting an armed terrorist to protect others and Parliament".
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Gallantry awards have also been conferred upon Bernard Kenny,a 78-year-old man who went to the aid of murdered Labour MP Jo Cox last year.
Police officers - Craig NichollsandJonathan Wright - who arrested Cox's killer, Thomas Mair, have also been awarded the Queen's Gallantry Medal.
This year's honours list is being hailed as the most diverse ever to mark the centenary of the awards.