1976: Nigeria Boycotts Olympics.

The 21st Olympic games in Montreal Canada saw the first organized widespread boycott in sports. 28 mostly African countries refused to take part including Nigeria.  

The target of their boycott was ultimately apartheid-era South Africa, but in this instance New Zealand were the proxy. The All Blacks were continuing to tour South Africa to play rugby in defiance of a general ban on sporting contact, which also included South Africa's exclusion from the Olympic movement.

The African nations leading the boycott wanted New Zealand also excluded.

The IOC’s argument was that the actions of New Zealand's rugby administrators were beyond their control.

Most of these protesting countries had accepted invitations to the games but had decided to withdraw after competitions had started, leaving the organizers with a major dilemma. They had no choice but to re schedule and cancel many events.

This was the first use of a boycott en masse as a political tool. 

The Video
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Major General Olufemi Olutoye, Head of the Nigerian Olympic team addresses a media conference to advise that the Nigerian team is withdrawing from the Olympic games. He explains that the committee feels they cannot take part in a competition where New Zealand is also appearing.