The men's 400 metre freestyle event at the 2001 World Aquatics Championships took place 22 July. Both the heats and final were held on 22 July.

In the final, Australian swimmer Ian Thorpe broke his own world record with a time of 3:40.17, bettering his previous record of 3:40.59 and successfully defending his world title. At the 200 metre mark in this race, Thorpe was over a second outside world record pace but had a split of 53.78 in the last 100 metres to break the record. This was the first of six gold medals he would win, and the first of four world records he would set at these championships.

Records Prior to the competition, the existing world and championship records were as follows: World record 3:40.59 Sydney, Australia 16 September 2000Championship record 3:43.80 Rome, Italy 9 September 1994

The following record was established during the competition: DateRoundNameNationalityTimeRecord 22 July Final Ian Thorpe 3:40.17 WR

Results

Preliminaries Rank Swimmer Nation Time Notes 1 Grant Hackett 3:44.88 Q 2 Ian Thorpe 3:45.22 Q 3 Emiliano Brembilla 3:46.45 Q 4 Massimiliano Rosolino 3:47.92 Q 5 Chad Carvin 3:49.93 Q 6 Shunichi Fujita 3:50.36 Q 7 Spyridon Gianniotis 3:50.98 Q 8 Dragoș Coman 3:50.99 Q 9 Athanasios Oikonomou 3:51.64 10 Jacob Carstensen 3:52.23 11 Rick Say 3:52.55 12 James Salter 3:52.72 13 Alexey Filipets 3:52.88 14 Heiko Hell 3:54.06 15 Edward Sinclair 3:54.52 16 Robert Margalis 3:54.65 17 Han Kyu-Chul 3:54.82 18 Nicolas Rostoucher 3:55.24 19 Masato Hirano 3:55.91 20 Andrew Hurd 3:56.45 21 Květoslav Svoboda 3:56.59 22 Ricardo Monasterio 3:56.96 23 Leonardo Salinas 4:00.47 24 Stepan Ganzey 4:01.01 25 Jorge Carral 4:01.10 26 Shilo Ayalon 4:02.06 27 Giancarlo Zolezzi 4:03.19 28 Jiang Bing-Ru 4:07.55 29 Mohammad Naeem Masri 4:19.60 30 Hsu Kuo-Tung 4:21.87 31 Barnsley Albert 4:25.09 32 Mumtaz Ahmad 4:32.10 33 Semen Danilov 4:35.17 34 Kin Duenas 4:38.72 35 Dean Palacios 4:38.99 36 Mark Unpingco 4:41.92 37 Zaid Saeed 4:50.64 – Thamer Al Shamroukh DNS

Final Rank Name Nationality Time Notes Ian Thorpe 3:40.17 WR Grant Hackett 3:42.51 Emiliano Brembilla 3:45.11 4 Massimiliano Rosolino 3:45.41 5 Chad Carvin 3:50.11 6 Dragoș Coman 3:50.13 7 Spyridon Gianniotis 3:52.09 8 Shunichi Fujita 3:52.11 Key: WR = World record

References