Nicholas Crace, from Overton in Hampshire, is also the oldest “altruistic” kidney donor – he will never meet the recipient of his organ.
He said: “It’s nice to feel in old age that one can still be useful.”
His surgeon said a kidney from a live donor “performs better, works quicker and lasts longer”.
Mr Crace, who enjoys visiting friends, gardening and volunteering, made the decision to donate last year in the months after his wife, Brigid, died.
He said he was no longer able to donate blood after turning 70 and when he looked at donating bone marrow he found out he needed to be under 40.
However, there was no age limit for kidneys, even “from somebody as ancient as me”, he said.