Fiona Julia O'Sullivan (born 17 September 1986) is a former footballer who played as a striker for clubs in the United States, Sweden, France, Germany and for English FA WSL team Notts County.

Born and raised in the United States to an Irish father, she has been capped for the Republic of Ireland women's national team.

O'Sullivan holds the record for career goals at the school,[5] including a brace in a rivalry match against undefeated Marin Catholic in 2004.

[6] Her most successful varsity campaign was 2006, as she finished team top-scorer with five goals despite missing half the season with a knee injury.

[9] In the 2010 WPS Draft, O'Sullivan was selected by the Chicago Red Stars,[7] but after attending their preseason training camp, was released from the initial 26-player roster in March 2010.

In January 2015 Notts County coach Rick Passmoor praised O'Sullivan's impact as she signed a one-year contract extension.

She featured as an 83rd-minute substitute in the 2015 FA Women's Cup Final at Wembley Stadium, which County lost 1–0 to Chelsea.

By then she had already agreed to quit professional soccer, to return to her alma mater as an assistant coach of the San Francisco Dons.

On the advice of her boyfriend, O'Sullivan sent an email to the FAI advising them of her eligibility for the Republic of Ireland women's national football team.

[27] After the initial flurry of goals O'Sullivan's form deteriorated and coach Susan Ronan eventually left her out of a squad in 2012.

Ronan later recalled O'Sullivan and praised her response to being dropped: "she has come back stronger, hungrier and fitter than she's ever been, so credit to her".

O'Sullivan missed Ireland's 2013 Cyprus Cup campaign with a knee injury sustained while training with her German club.

[30] Despite three goals from O'Sullivan, Ireland's 2015 FIFA Women's World Cup qualification campaign ended in failure.

However, it was an emotional curtain call for O’Sullivan, who played in front of those who had supported her since her days at Sir Francis Drake High School.

Although I am Irish, I grew up in San Geronimo and I have such a huge family here who has supported me through high school, college, and came to all my games,” O’Sullivan said.