A competição dos 400 metros rasos masculino nos Jogos Olímpicos de Verão de 2008 aconteceu no dias 18 a 21 de Agosto no Estádio Nacional de Pequim.
Recordes Antes desta competição, os recordes mundiais e olímpicos da prova eram os seguintes:
Resultados Ronda 1 Eliminatória 1 #LaneAtleta/PaísTempoNotasReact1445.12 Q. 0.1902545.22 Q. 0.1893645.37 Q(SB)0.1804845.43 Q. 0.1496345.89 . 0.2497746.06 . 0.2098246.29 (SB)0.183945.52DSQ0.299
Eliminatória 2 #LaneAtleta/PaísTempoNotasReact1644.79 Q. 0.2052744.80 Q(PB)0.1553444.81 Q(SB)0.2294544.89 Q(SB)0.1845845.66 . 0.1776946.28 . 0.2367348.54 (SB)0.2098253.11 . 0.245
Eliminatória 3 #LaneAtleta/PaísTempoNotasReact1845.36 Q. 0.1962345.49 Q. 0.2003945.96 Q. 0.2254746.32 (SB)0.1615646.60 . 0.1586246.76 . 0.2447446.79 . 0.2128547.12 . 0.247
Eliminatória 4 #LaneAtleta/PaísTempoNotasReact1745.00 Q. 0.2072845.17 Q(PB)0.1823545.22 Q. 0.2114346.10 . 0.2465946.34 . 0.2656246.38 . 0.1577646.39 . 0.225. 4DNS.
Eliminatória 5 #LaneAtleta/PaísTempoNotasReact1244.96 Q. 0.2142745.19 Q. 0.1723845.25 Q(PB)0.1864345.25 Q(PB)0.2255645.63 . 0.1956946.15 . 0.2157546.59 . 0.2688447.89 . 0.288
Eliminatória 6 #LaneAtleta/PaísTempoNotasReact1744.94 Q(PB)0.2482545.13 Q. 0.2663645.17 Q(PB)0.1934845.56 . 0.2045245.67 . 0.1726346.30 . 0.1987946.46 . 0.3478447.83 . 0.260
Eliminatória 7 #LaneAtleta/PaísTempoNotasReact1945.23 Q. 0.2532645.36 Q(NR)0.1653245.54 Q. 0.2034445.83 . 0.2755546.03 . 0.1946346.28 . 0.2607747.10 . 0.2078849.08 . 0.178
Semi-finais Semi-final 1 #LaneAtleta/PaísTempoNotasReact1644.15 Q. 0.2242544.59 Q. 0.2443644.88(NR)0.1624744.98(NR)0.1695445.02 (SB)0.1686245.06 (PB)0.1917845.19 (NR)0.1658245.64 . 0.259
Semi-final 2 #LaneAtleta/PaísTempoNotasReact1644.79 Q(SB)0.1592444.91 Q. 0.1903545.06. 0.1874945.09. 0.2205345.11 (PB)0.1916845.24 . 0.1857245.52 . 0.1968745.59 . 0.216
Semi-final 3 #LaneAtleta/PaísTempoNotasReact1744.12 Q. 0.1872644.60 Q(PB)0.1263844.64 q(SB)0.2114544.82 q(PB)0.2045244.94 . 0.1876945.56 . 0.2037445.56 . 0.2058345.81 . 0.199
Final thumb|300px|Atletas cruzando a meta # Pista Nome PaísTempo Tempo de Reação Notas 4 LaShawn Merritt 43.75 0.318 PB 7 Jeremy Wariner 44.74 0.209 9 David Neville 44.80 0.293 4 5 Chris Brown 44.84 0.231 5 6 Leslie Djhone 45.11 0.164 6 8 Martyn Rooney 45.12 0.208 7 2 Renny Quow 45.22 0.201 8 3 Johan Wissman 45.39 0.218
200m masculino