1991 IAAF World Indoor Championships – Men's 400 metres

The men's 400 metres event at the 1991 IAAF World Indoor Championships was held on 8, 9 and 10 March.

Heats
First 2 of each heat (Q) and next 4 fastest (q) qualified for the semifinals.

Semifinals
First 3 of each semifinal (Q) qualified directly for the final.