2012 World Junior Championships in Athletics – Men's 800 metres

The men's 800 metres at the 2012 World Junior Championships in Athletics was held at the Estadi Olímpic Lluís Companys on 13, 14, and 15 July.

Records
, the existing world junior and championship records were as follows.

Heats
Qualification: The first 3 of each heat (Q) and the 3 fastest times (q) qualified

Semi-final
Qualification: The first 2 of each heat (Q) and the 2 fastest times (q) qualified

Participation
According to an unofficial count, 60 athletes from 41 countries participated in the event. • undefined (2)

• 🇦🇺 australia (2)

• 🇦🇹 austria (2)

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• 🇧🇪 belgium (2)

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• 🇨🇦 canada (2)

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• 🇨🇰 cook islands (1)

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• 🇨🇾 cyprus (1)

• 🇪🇹 ethiopia (2)

• 🇩🇪 germany (2)

• 🇮🇪 ireland (2)

• 🇮🇹 italy (2)

• 🇯🇵 japan (2)

• 🇰🇪 kenya (2)

• 🇲🇦 morocco (1)

• 🇲🇿 mozambique (1)

• 🇳🇿 new zealand (2)

• 🇳🇴 norway (2)

• 🇵🇱 poland (1)

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• 🇶🇦 qatar (2)

• 🇷🇴 romania (1)

• 🇷🇸 serbia (1)

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• 🇪🇸 spain (2)

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• 🇸🇪 sweden (1)

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• 🇹🇷 turkey (1)

• 🇺🇦 ukraine (1)

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• 🇺🇸 united states (2)

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• 🇾🇪 yemen (1)