The 79-year-old former miner’s death was confirmed tonight by his son, Phil Kenny.
He is reported to have been suffering from cancer.
Mr Kenny was stabbed in the chest as he courageously tried to go to the aid of Mrs Cox during the attack in Birstall that claimed her life in June last year.
A victim statement read on his behalf as Mrs Cox’s killer, Thomas Mair, stood trial said: “What you did to me that Thursday afternoon not only threatened my life but changed me as a person and all those around me.”
Mr Kenny was awarded the George Medal in this year’s Queen’s Birthday Honours List.