Swimming at the 2009 SEA Games – Women's 400 metre individual medley

The Women's 400 Individual Medley (or "I.M.") swimming event at the 2009 SEA Games was held in December 2009.

The Games Record at the start of the event was 4:51.87, swum by Joscelin Yeo at the 1999 SEA Games (on August 13).