2009 World Youth Championships in Athletics – Boys' 400 metres
The Boys' 400 metres at the 2009 World Youth Championships in Athletics was held at the Brixen-Bressanone Sport Arena on 8, 9, and 10 July. The event was won by Kirani James of the Grenada, who also won the 200 metres.Medalists
Records
Prior to the competition, the following records were as follows.
Kirani James set a new Championship Record and World Youth Leading in the final.Heats
Qualification rule: first 2 of each heat plus the 4 fastest times qualified.Semifinals
Qualification rule: first 2 of each heat plus the 2 fastest times qualified.Key: PB = Personal best, SB = Seasonal bestHeat 2
Key: PB = Personal best, SB = Seasonal bestHeat 3
Key: PB = Personal best, SB = Seasonal bestFinal
| Rank | Lane | Name | Nationality | Time | Notes |
| 3 | Kirani James | | 45.24 | PB, CR, WYL |
| 4 | Joshua Mance | | 46.22 | PB |
| 6 | Awad El Karim Makki | | 47.15 | SB |
| 2 | Nathan Wake | | 47.20 | |
| 7 | Frazer Wickes | | 47.66 | |
| 5 | Javere Bell | | 47.89 | PB |
| 1 | Shogo Momiki | | 48.01 | |
| 8 | Varg Königsmark | | 48.12 | |
Key: PB = Personal best, SB = Seasonal best, CR = Championship record, WYL = World Youth Leading
