Konkurrencen i 4 x 100m fri for kvinder blev afholdt 28. juli i Aquatics Centre London.^[1]

Inden konkurrencen var verdensrekorden og den olympiske rekord følgende:

Verdensrekord	Holland Inge Dekker (53.61) Ranomi Kromowidjojo (52.30) Femke Heemskerk (53.03) Marleen Veldhuis (52.78)	3:31.72	Rom, Italien	26. juli 2009
Olympisk rekord	Holland Inge Dekker (54.37) Ranomi Kromowidjojo (53.39) Femke Heemskerk (53.42) Marleen Veldhuis (52.58)	3:33.76	Beijing, Kina	10. august 2008

Følgende rekord blev opnået under konkurrencen

Olympisk rekord

Australien Alicia Coutts (53.90) Cate Campbell (53.19) Brittany Elmslie (53.41) Melanie Schlanger (52.65)

3:33.15

28. juli 2012

Ranc.	Heat	Bane	Nationalitet	Navne	Tid	Noter
1	2	3	Australien	Emily Seebohm (54.24) Brittany Elmslie (53.41) Yolane Kukla (54.61) Libby Trickett (54.08)	3:36.34
2	1	4	USA	Lia Neal (54.15) Amanda Weir (54.37) Natalie Coughlin (54.08) Allison Schmitt (53.86)	3:36.53
3	2	4	Holland	Marleen Veldhuis (54.73) Inge Dekker (53.79) Hinkelien Schreuder (55.62) Femke Heemskerk (53.59)	3:37.76
4	1	6	Kina	Tang Yi (53.86) Qiu Yuhan (54.85) Wang Haibing (54.14) Wang Shijia (55.06)	3:37.91
5	1	5	Japan	Haruka Ueda (54.22) Yayoi Matsumoto (54.23) Miki Uchida (54.47) Hanae Ito (55.14)	3:38.06
6	2	2	Danmark	Pernille Blume (54.44) Mie Nielsen (54.49) Lotte Friis (55.97) Jeanette Ottesen Gray (53.19)	3:38.09
7	1	2	Storbritannien	Amy Smith (54.29) Jess Lloyd (54.53) Caitlin McClatchey (54.64) Rebecca Turner (54.75)	3:38.21
8	1	3	Sverige	Sarah Sjöström (54.31) Michelle Coleman (54.14) Ida Marko-Varga (54.57) Gabriella Fagundez (55.19)	3:38.21
9	2	5	Tyskland	Britta Steffen (54.43) Silke Lippok (55.30) Lisa Vitting (54.77) Daniela Schreiber (54.66)	3:39.16
10	1	7	Rusland	Veronika Popova (54.30) Nataliya Lovtsova (55.00) Viktoriya Andreyeva (55.27) Margarita Nesterova (55.02)	3:39.59
11	2	6	Canada	Victoria Poon (54.67) Julia Wilkinson (54.38) Samantha Cheverton (54.93) Heather Maclean (55.62)	3:39.60
12	2	7	Italien	Alice Mizzau (55.17) Federica Pellegrini (54.28) Laura Letrari (55.74) Erika Ferraioli (54.55)	3:39.74
13	1	8	Hviderusland	Aleksandra Gerasimenya (53.85) Svetlana Khokhlova (54.96) Oksana Demidova (55.94) Yuliya Khitraya (55.92)	3:40.67
14	2	1	New Zealand	Tash Hind (55.93) Penelope Marshall (55.82) Amaka Gessler (55.77) Hayley Palmer (55.03)	3:42.55
15	1	1	Ungarn	Ágnes Mutina (56.05) Evelyn Verrasztó (55.80) Éva Risztov (57.81) Eszter Dara (55.13)	3:44.79
16	2	8	Grækenland	Theodora Drakou (55.42) Nery Mantey Niangkouara (55.52) Theodora Giareni (57.26) Kristel Vourna (57.35)	3:45.55

Ranc.	Bane	Nationalitet	Navne	Tid	Noter
1 Guld	4	Australien	Alicia Coutts (53.90) Cate Campbell (53.19) Brittany Elmslie (53.41) Melanie Schlanger (52.65)	3:33.15	OR
2 Sølv	3	Holland	Inge Dekker (54.67) Marleen Veldhuis (53.80) Femke Heemskerk (53.39) Ranomi Kromowidjojo (51.93)	3:33.79
3 Bronze	5	USA	Missy Franklin (53.52) Jessica Hardy (53.53) Lia Neal (53.65) Allison Schmitt (53.54)	3:34.24	AM, NR
4	6	Kina	Tang Yi (53.58) Qiu Yuhan (54.49) Wang Haibing (54.03) Pang Jiaying (54.65)	3:36.75
5	8	Storbritannien	Amy Smith (54.27) Francesca Halsall (53.29) Jess Lloyd (54.65) Caitlin McClatchey (54.81)	3:37.02
6	7	Danmark	Pernille Blume (54.52) Mie Nielsen (54.04) Lotte Friis (55.72) Jeanette Ottesen Gray (53.24)	3:37.45
7	2	Japan	Haruka Ueda (54.34) Yayoi Matsumoto (54.52) Miki Uchida (54.43) Hanae Ito (54.67)	3:37.96
–	1	Sverige	Michelle Coleman (54.57) Sarah Sjöström (53.91) Ida Marko-Varga (55.01) Gabriella Fagundez	DISK