Kenya's David Rudisha caused a sensation in the main Olympic stadium on Thursday by winning the 800m in a new world record time of 1min 40.91s.
Rudisha broke the record mark of 1min 41.01s he set in 2010.
Nijel Amos, of Botswana, won silver in 1min 41.73s, while bronze went to Kenyan Timothy Kitum in 1min 42.53s.
Rudisha, 23, is the first Olympic champion from his Maasai tribe. His father Daniel won a silver in the 4x400m relay at the Mexico Games in 1968.