Genghis Khan or Chengiz Khan was the first Great Mongolian tribal chief who conquered northern China, Central Asia (including Kazakhstan, Uzbekistan, Turkmenistan), Afghanistan and invaded parts of India (modern-day Pakistan). Iran, Azerbaijan, Georgia, and large swathes of Russian lands were also integrated into the Mongol Empire. Even Europe was afraid of him.
Genghis Khan established the 2nd largest empire in the world after the British Empire. His empire was also the largest contiguous empire in the world. He was the founder of modern-day Mongolia, He also captured Beijing, Samarkand, Balkh, Bukhara, Bamyan, Herat. His grandson Kublai Khan ruled over entire China and captured the Sung dynasty.