Doreen Kenny will receive the George Medal awarded to her late husband Bernard for attempting to save the life of murdered Batley and Spen MP Jo Cox.
The former miner died before he could collect his honour, awarded for his bravery after he was stabbed as he intervened when Thomas Mair attacked Mrs Cox in his home village of Birstall, West Yorkshire, in June 2016.
After Mrs Cox's murder there were numerous calls for Mr Kenny to be honoured, including a petition aimed at securing him the George Cross - the highest possible civilian honour.
At Mair's trial at the Old Bailey, the jury heard that the pensioner was waiting for his wife outside the library in Birstall when he saw Mair going "berserk".
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He said in a statement to police: "I thought if I could jump on to the back, I could take him down.
"I thought he was thumping her until I saw the blood. I saw he had a knife in his hands. It was what I call a dagger. The blade was about nine inches.
"Just as I got short of him, he turned around and saw me. He shoved the knife in and it hit me in the stomach. The blood started pouring out between my fingers. I saw the blood and I thought 'Oh my God'."
Mr Kenny described Mair's actions as a "pure act of evil".
After the attack, more than 80,000 people signed an online petition calling for Mr Kenny to be awarded the George Cross for his bravery.
Mr Kenny, who shared a birthday with Mrs Cox, worked as a miner for 40 years and was a former member of the Gomersal Mines Rescue team, which tried to save victims of the Lofthouse mine disaster in 1973.
Neo-Nazi Mair was given a whole life sentence for the murder of Mrs Cox, and was also found guilty of causing grievous bodily harm to Mr Kenny and possession of a gun and dagger.
At the same investiture ceremony actress Julie Walters will be made a dame and Helen McCrory will be made an OBE.
Walters will receive the honour for services to drama, almost 35 years after her breakout role in Educating Rita, for which she was nominated for an Oscar.
Since then she has bagged a second Academy Award nomination for her turn in Billy Elliot and has had starring roles in films including Mamma Mia, Calendar Girls, Brave and seven of the eight Harry Potter films, playing Molly Weasley.
On the small screen she is best known for her collaborations with the late Victoria Wood, including Wood And Walters and Dinnerladies.
She was named Dame Commander of the Order of the British Empire (DBE) in the 2017 Birthday Honours.
Peaky Blinders star Helen McCrory, who also starred in Harry Potter as Narcissa Malfoy - the mother of Draco, will be honoured for services to drama.