This world record is interesting because it may be that we will never know who really, truly has the highest IQ. According to the Guinness Book of World Records, it is Marilyn Vos Savant:
In 1985, Guinness World Records accepted that she had answered every question correctly on an adult Stanford-Binet IQ test at the age of just 10, a result that gave her a corresponding mental age of 22 years and 11 months, and an unearthly IQ of 228.
For many people, the story of Savant and “Ask Marilyn” are just two more pieces of evidence in a larger, decades-long argument about the accuracy and objectivity of intelligence testing. Even Guinness has succumbed. In 1990, two years after inducting Savant into its Hall of Fame, the publisher, in its parlance, “rested” its high IQ category altogether, saying it was no longer satisfied that intelligence tests were either uniform or reliable enough to produce a single record holder. Depending on how you look at it, Savant will either never be beaten, or was not worth beating in the first place.
Here is another person who is up there in terms of IQ scores - Christopher Langan:
One researcher says his IQ is "unmeasurable". Another estimates 195.
The article also mentions Ron Hoeflin:
In between conversations with Marilyn vos Savant, I also spent time in New York with a man called Ron Hoeflin. Hoeflin is two years older than Savant, also from St Louis, and also has a remarkable IQ score – 190 – yet has frustratingly little to show for it. He lives only a few blocks from Savant's penthouse, above a café/Laundromat, and describes himself as self-employed.
It's an interesting article, for sure.