The women's 400 metres event at the 2021 European Athletics Indoor Championships was held on 5 March 2021 at 11:22 (heats) and at 19:33 (semi-finals), and on 6 March 2021 at 20:25 (final) local time.

Having run 50.64 earlier in the winter, the fastest time by a European woman since 2009, Femke Bol entered the Championships as the overwhelming favorite. Her Dutch teammate, Lieke Klaver, was the second-fastest European woman of the indoor season with 51.21, a top 5 time by a European woman in the last ten years and over half a second faster than the third fastest woman of the season. Other contenders who ran under 52 seconds prior to the Championships included 2019 European indoor and world outdoor finalist Justyna Święty-Ersetic, 2016 European Youth Champion and 2019 European U23 bronze medallist Andrea Miklos and the Irish 100m and 200m outdoor national record holder Phil Healy. The defending 2019 champion Léa Sprunger was the 13th fastest European woman of the indoor season going into the Championships.

All five women who ran under 52 seconds prior to the Championships made the final. The surprise sixth spot went the British 200m specialist Jodie Williams, who was contesting her first 400m at a major Championships. Starting in lane 6, Bol took her first 100m conservatively, and her Dutch teammate Klaver was the first one at the break. Bol took the lead at the back straight of the second lap, and by the 300m mark it was Bol, followed by Klaver and Święty-Ersetic. The last 50m saw Klaver tie up, with Święty-Ersetic moving into second place and Williams into third. Bol's winning time of 50.63 was a 0.01 second improvement of her own National Record and the fastest winning time at the European Indoor Championships since 2007. It was Bol's first international senior individual medal. Three finalists set personal bests in the final.

Heats

Qualification: First 2 in each heat (Q) and the next fastest 4 (q) advance to the Semifinals.^[1]

More information Rank, Heat ...

Rank	Heat	Athlete	Nationality	Time	Note
1	5	Phil Healy	Ireland	52.00	Q
2	3	Justyna Święty-Ersetic	Poland	52.06	Q
3	3	Jessie Knight	Great Britain	52.17	Q, SB
4	5	Léa Sprunger	Switzerland	52.25	Q
5	3	Cynthia Bolingo Mbongo	Belgium	52.27	q, SB
6	4	Jodie Williams	Great Britain	52.35	Q
7	5	Modesta Justė Morauskaitė	Lithuania	52.52	q, PB
8	4	Andrea Miklós	Romania	52.57	Q
9	6	Ama Pipi	Great Britain	52.63	Q, SB
10	3	Kateryna Klymyuk	Ukraine	52.70	q, PB
11	5	Rebecca Borga	Italy	52.72	q
12	4	Alice Mangione	Italy	52.73	PB
13	2	Lieke Klaver	Netherlands	52.74	Q
14	7	Irini Vasiliou	Greece	52.76	Q, PB
15	2	Anna Ryzhykova	Ukraine	52.76	Q
16	1	Femke Bol	Netherlands	52.77	Q
17	6	Lisanne de Witte	Netherlands	52.82	Q, =SB
18	6	Lada Vondrová	Czech Republic	52.83
19	1	Hanna Mikhailava	Belarus	52.96	Q
20	7	Agnė Šerkšnienė	Lithuania	53.00	Q
21	1	Laura Müller	Germany	53.03
22	6	Corinna Schwab	Germany	53.06
23	7	Amandine Brossier	France	53.23
24	3	Cátia Azevedo	Portugal	53.28	SB
25	3	Maja Ćirić	Serbia	53.28	SB
26	2	Sophie Becker	Ireland	53.31
27	4	Susanne Walli	Austria	53.41	PB
28	1	Tereza Petržilková	Czech Republic	53.46
29	7	Anastasiia Bryzgina	Ukraine	53.50
30	5	Hanne Maudens	Belgium	53.63
31	4	Aauri Lorena Bokesa	Spain	53.64
32	2	Camille Laus	Belgium	53.68
33	7	Sharlene Mawdsley	Ireland	53.68
34	4	Iveta Putalová	Slovakia	53.69	SB
35	2	Eleonora Marchiando	Italy	53.70
36	2	Krystsina Muliarchik	Belarus	53.93
37	1	Andrea Jiménez	Spain	54.34
38	1	Silke Lemmens	Switzerland	54.48
39	6	Evelin Nádházy	Hungary	55.11

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Semifinals

Qualification: First 2 in each heat (Q) advance to the Final.^[2]

More information Rank, Heat ...

Rank	Heat	Athlete	Nationality	Time	Note
1	3	Femke Bol	Netherlands	51.17	Q
2	2	Justyna Święty-Ersetic	Poland	51.34	Q, NR
3	2	Lieke Klaver	Netherlands	52.09	Q
4	3	Jodie Williams	Great Britain	52.09	Q, PB
5	2	Anna Ryzhykova	Ukraine	52.11	PB
6	2	Jessie Knight	Great Britain	52.22
7	1	Phil Healy	Ireland	52.41	Q
8	1	Andrea Miklós	Romania	52.41	Q
9	1	Amarachi Pipi	Great Britain	52.54	SB
10	3	Léa Sprunger	Switzerland	52.64
11	2	Agnė Šerkšnienė	Lithuania	53.09
12	1	Lisanne de Witte	Netherlands	53.10
13	1	Kateryna Klymyuk	Ukraine	53.10
14	1	Hanna Mikhailava	Belarus	53.10
15	3	Modesta Justė Morauskaitė	Lithuania	53.20
16	3	Irini Vasiliou	Greece	53.31
17	3	Cynthia Bolingo Mbongo	Belgium	53.74
18	2	Rebecca Borga	Italy	54.23

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Final

^[3]

More information Rank, Lane ...

Rank	Lane	Athlete	Nationality	Time	Note
	6	Femke Bol	Netherlands	50.63	EL, NR
	5	Justyna Święty-Ersetic	Poland	51.41
	1	Jodie Williams	Great Britain	51.73	PB
4	4	Phil Healy	Ireland	51.94	PB
5	3	Lieke Klaver	Netherlands	52.03
6	2	Andrea Miklós	Romania	52.10

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