Top 12 People with Highest IQ in the World - Listovative https://listovative.com/top-12-people-highest-iq-world/ 1. William James Sidis (IQ Level- 250-300) Sidis had exceptional mathematical abilities. At 6, he went to a grammar school and in 7 months he had graduated. He attended Harvard at the age of 11 and mastered over 40 languages. He was threatened by some fellow students in Harvard so his parents assigned him on a teaching job in Texas. But soon he left the job and started concentrating on a political career.