Swimming at the 2012 Summer Olympics – Women's 100 metre freestyle

The women's 100 metre freestyle event at the 2012 Summer Olympics took place on 1–2 August at the London Aquatics Centre in London, United Kingdom.

Dutch swimmer Ranomi Kromowidjojo blasted a new Olympic record to become the country's third gold medalist in the event since Rie Mastenbroek topped the podium in 1936 and Inge de Bruijn in 2000. Flipping fourth at the halfway turn, she pulled ahead of a tightly-packed field to touch the wall first and improve her own record in 53.00. Belarus' Aliaksandra Herasimenia strengthened her lead on the first length under a world-record pace, but faded down the stretch to pick up a silver in 53.38. Meanwhile, China's Tang Yi produced a fast burst on the final lap to capture the bronze in 53.44.

Australia's Melanie Schlanger finished fourth in 53.47, while American teenage sensation Missy Franklin denied a chance for another Olympic medal with a fifth-place time in 53.64. Great Britain's home favorite Francesca Halsall (53.66), Denmark's Jeanette Ottesen (53.75), who shared the title with Herasimenia at the 2011 World Championships, and U.S. swimmer Jessica Hardy (54.02) rounded out the finale.

Before the breakthrough finale, Kromowidjojo threw down a top-seeded time of 53.05 to slice 0.07 seconds off the previous Olympic record set by Germany's defending champion Britta Steffen, who later missed the final roster with a twelfth-place finish (54.18) from the semifinals.

Among the fifty swimmers registered in the event, only forty-eight had competed. Sweden's five-time Olympian Therese Alshammar suffered from a pinched nerve in her neck, and decided to skip most of her events. Additionally, Australia's Cate Campbell scratched her first individual race because of a glandular fever.