1. William James Sidis
IQ level: 250 – 300
Nationality: American
2. Terence Tao
IQ level: 225-230
Nationality: Australian
3. Christopher Hirata
IQ level: 225
Nationality: American
4. Kim Ung-Yong
IQ level: 210
Nationality: American, currently South Korean
5. Garry Kasparov
IQ level: 194
Nationality: Russian and formerly a citizen of the Soviet Union