It's in a results page somewhere, but there was a man who won the silver medal in the Olympics as a forty-one year old.

When eligibility was being changed (reinstatements allowed) the Protopopovs (this was actually written in Sandra Bezic's book) considered making a run for Swiss nationals (since they have since become Swiss citizens) and maybe making the Olympics. They would've made it in their...late fifties/early sixties!