Here you can find the list of countries that participated in Olympics 2012 in London.
The 2012 Summer Olympics medal table is a list of National Olympic Committees (NOCs) ranked by the number of gold medals won during the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. Approximately 10,800 athletes participated in 302 events in 26 sports.
Each country selected the best participants they had.
To qualify for the Olympics there are 3 stages: first stage is gaining a qualification controlled by the International Olympic Committee and International sporting Federation, second stage is nomination