Nelson Charles Dellis (born February 4, 1984) is an American memory athlete, Grandmaster of Memory, mountaineer, published author, public speaker, and consultant.
He is a four-time USA Memory Champion, tying the record for most wins of the national memory champion title.
He is also one of the co-founders of Memory League (formerly, Extreme Memory Tournament).
Nelson also runs Climb 4 Memory - a nonprofit which "aims to raise funds and awareness for Alzheimer's disease research through mountain climbs around the world."