Coughlin was born in Vallejo, California, and is of Irish and one quarter Filipino ancestry.Coughlin first began swimming at the local YMCA when she was only 10 months old. Catherine of Siena School in Vallejo, for kindergarten through eighth grade, and then Carondelet High School in Concord, California.Swimming in lane eight, Coughlin set the American record with a time of .43, to break Katie Hoff's one-day-old record of .09.
Coughlin won her third gold medal in the women's 100-meter freestyle with a time of 53.99.
She won her fourth gold medal in the women's 4×200-meter freestyle relay with Elizabeth Hill, Diana Munz, and Lindsay Benko.
The following day, Coughlin finished in 4th place in the 100-meter freestyle despite setting the championship record in the semi-finals.
In her last event, the 4×100-meter medley relay, Coughlin won a silver medal along with Tara Kirk, Rachel Komisarz, and Lacey Nymeyer.
Coughlin won her silver medal in the women's 4×100-meter medley relay, teaming up with Megan Quann, Mary Descenza, and Erin Phenix; the Australians won the gold (Calub, Jones, Thomas, Ryan).
Coughlin won her bronze medal in the 50-meter backstroke; fellow American Haley Cope won gold and Antje Buschschulte won the silver.
While in high school in 1998, she became the first swimmer to qualify for the Summer National in all fourteen events.
Coughlin broke two individual national high school records in the 200-yard individual medley (.45) and the 100-yard backstroke (52.86). Coughlin attended the University of California, Berkeley, where she swam for coach Teri Mc Keever's California Golden Bears swimming and diving team in National Collegiate Athletic Association (NCAA) competition from 2001 to 2003.
Coughlin's success has earned her the World Swimmer of the Year Award one time and American Swimmer of the Year Award three times.