Denise O'Sullivan

Peamount United and Cork After her performance in the 2011 FAI Women's Cup final, O'Sullivan signed with Peamount United, ahead of their 2011–12 UEFA Women's Champions League campaign. She made three appearances in the Champions League for the South Dublin club, before returning to her hometown and joining newly founded Cork Women's FC, one of the six teams that competed in the Women's National League's (WNL) inaugural 2011–12 season. On 13 November 2011, she made her debut in a 6–1 loss to Peamount United. In her first season, she scored six goals in 15 appearances and was named to the league's Best XI. In July 2012, O'Sullivan re-joined Peamount United and made three appearances in the Champions League, scoring a goal in a 4–0 victory against Cardiff Metropolitan. and finished her second season with two goals in 11 appearances.

Glasgow City On 10 July 2013, O'Sullivan joined Scottish champions Glasgow City, ahead of their 2013–14 UEFA Women's Champions League campaign. She scored on her league debut, on 28 July, in a 2–0 win over Rangers. On 8 August, she made her Champions League debut for the club in a 7–0 home victory against ŽNK Osijek. Her goal in a 3–1 win over Standard Liège on 17 October helped Glasgow City progress into the last 16 of the Champions League. On 16 November, it was announced that O'Sullivan had signed new contract with the club. She finished the 2013 season with three goals in 12 appearances in all competitions.

O'Sullivan made nine appearances in the 2014–15 UEFA Women's Champions League campaign and scored four goals, including a brace in a 4–0 victory against Zhytlobud-1 Kharkiv on 14 August 2014. After lifting the domestic treble and being part of the first Scottish team to ever reach the quarter-finals of the Champions League, she was voted SWPL Players' Player of the Year. On 16 December 2014, she signed a new two-year contract with Glasgow City. In August 2015, she was named SWPL Player of the Month. She was also named Glasgow City Players' Player of the Year, Coaches' Player of the Year and Fans' Player of the Year in both 2014 and 2015.

Houston Dash

On 19 March 2016, O'Sullivan signed with the Houston Dash, who paid Glasgow an undisclosed "four figure" transfer fee, which was the first time a Scottish women's club was paid a compensation fee for a player. She made her first appearance during the 2016 season in a 0–0 home draw with Sky Blue on 30 April, coming on as a substitute in the 46th minute. On 7 May, she came on as a substitute at halftime and scored her first goal in a 2–1 away victory against 2015 champion FC Kansas City. She finished the 2016 season with 2 goals and 5 assists in 18 appearances.

North Carolina Courage On 28 July 2017, O'Sullivan was claimed off waivers by the North Carolina Courage. On 10 August, she made her debut in a 1–0 win over FC Kansas City. On 8 October, O'Sullivan scored the game-winning goal in the 89th minute of the semi-final against the Chicago Red Stars. She made a total of nine appearances for the Courage in 2017 and scored one goal. On 22 September, O'Sullivan played the entire match as the Courage won the NWSL Championship 3–0 over the Portland Thorns FC, the first time the Courage had won the title. O'Sullivan was named MVP by her team.

During the 2019 season, O'Sullivan was a starter in 22 of the 24 games she played. After defeating Reign FC 4–1 in the semi-finals, O'Sullivan helped lead the Courage win their second NWSL Championship shutting out the Chicago Red Stars 4–0 in the final. O'Sullivan started and played the entire match. Teammate Sam Mewis said O'Sullivan was 'the "glue" that holds the team together, winning tackles and spraying the ball wide from a deeper position.'

In November 2019, O'Sullivan signed a multi-year contract with the Courage. Head coach Riley said, "She is one of the first names on the team sheet every week. She is a massive influencer in the way we play. She has a genius soccer IQ that makes her a brilliant reader and manipulator of the game. She is a tremendous footballer and passer of the ball and she breaks up the opponent's playmaking ability with an intuitive reading of the game." However, she made only five appearances for the Courage in the pandemic-shortened 2020 season before going on loan to Brighton.

O'Sullivan played every minute of the preseason 2022 NWSL Challenge Cup, in which the Courage defeated the Washington Spirit 2–1 in the final. She made 19 appearances and 18 starts in the regular season as the Courage finished seventh, missing the playoffs.

O'Sullivan was named captain before the 2023 season. On April 19, 2023, she scored a last-minute goal against the Orlando Pride to draw 1–1 in the Challenge Cup group stage. She helped the Courage defend that title as they defeated Racing Louisville 2–0 in the final. She was named to the NWSL Best XI Second Team at the end of the season. She played and started in 20 games and scored 1 goal and ranked top five in the league in passing accuracy and duels won. North Carolina placed third in the league but lost to eventual champions NJ/NY Gotham FC in the quarterfinals.

On 29 July 2024, O'Sullivan's contract was extended to keep her with the Courage through the end of 2026. She played in 23 league games, starting 21, and scored 1 goal in 2024, as the Courage finished fifth in the league, losing to the Kansas City Current in the quarterfinals.

O'Sullivan played in 18 games and started 17 for the Courage in 2025, missing about two months with a knee injury. She made her first start since the injury in the season finale, playing the entire match in a 3–2 win over Gotham FC on 2 November 2025, as the Courage finished ninth and narrowly missed playoffs. As a guest player in the W-League, she is permitted to play seven non-consecutive games. On 28 October 2018, she made her debut in a 2–0 home victory against Melbourne City. The Sydney Morning Herald reported that O'Sullivan had been "a sensation" in her seven games for the club. She made her debut for the club on 22 November during a 1–0 against Newcastle Jets FC. O'Sullivan was a starting midfielder in all seven games that she played. Their fourth place finish earned the team a berth to the semi-finals where they were defeated 5–1 by eventual champions, Melbourne City.

In September 2020, O'Sullivan moved on loan to English FA WSL club Brighton & Hove Albion through 31 December 2020. She wanted to be available for Ireland's rescheduled UEFA Women's Euro 2022 qualifying Group I fixtures. Travelling back and forth from the United States would force her to undergo three separate two-week periods of quarantine within nine weeks. She made her debut for Brighton as a half-time substitute for fellow Corkonian Megan Connolly in a 0–0 draw at Manchester City on 13 September 2020. She was a starting midfielder in eight of the nine matches she played. Her transfer fee, reported in the range of £300,000, broke Liverpool's club record for a transfer fee paid, which previously stood at the £210,000 paid for Olivia Smith in 2024. She made her Reds debut on 18 January 2026 in a 6-0 Women's FA Cup victory over London Bees, scoring her first goal for the club after six minutes. She made her Women's Super League debut on 25 January 2026 in a 2-0 victory over Spurs, the team's first league victory of the season. O'Sullivan left Liverpool in July 2026 to join Gotham FC.

Gotham FC (loan)

On 14 July 2026, NWSL club Gotham FC announced that they had acquired O'Sullivan from Liverpool on an initial year-long loan deal with obligation to buy. O'Sullivan made her Gotham FC debut five days later, participating in a 3–2 come-from-behind victory over the Seattle Reign.

International career Youth

O'Sullivan was part of the under-17 team that finished in second place at the 2010 UEFA Women's Under-17 Championship, after losing on penalties in the final against Spain. At the 2010 FIFA U-17 Women's World Cup in Trinidad and Tobago, she scored in the quarter-final defeat against eventual runners-up Japan, after helping Ireland finish top of a group that included Brazil, Canada and Ghana.

Senior On 17 September 2011, O'Sullivan made her senior debut and scored both goals in a 2–0 UEFA Women's Euro 2013 qualifying Group 4 win over Wales in Newport. She headed Ireland into the lead over Scotland in their Euro 2013 qualifier at Tynecastle Stadium in April 2012, but the Scots staged a late comeback to win 2–1.

O'Sullivan continued to be selected by national team coach Susan Ronan and participated in Ireland's failed 2015 FIFA Women's World Cup qualification campaign. Alongside namesake Fiona O'Sullivan she was the team's joint-top goalscorer with three goals. She was named 2015 FAI Senior International Player of the Year.

She remained an important national team player under Ronan's successor Colin Bell, displaying good form in the unsuccessful 2019 FIFA Women's World Cup qualifying series.

Style of play O'Sullivan emerged as a promising forward with the Irish youth national teams. She developed into a midfield playmaker, described by her North Carolina Courage coach Paul Riley as one of the most "gifted and complete" in world football: "She has a massive impact on tactics because she controls the tempo, dictates the tempo and her job functions are multi-faceted."

O'Sullivan is noted as an aggressive player and was nicknamed "junkyard" by her coach. In November 2019, Ireland's head coach Vera Pauw declared O'Sullivan one of the best players in the world: "There is no player in the world at this moment that is a playmaker but also the motor in winning the ball back. She has everything."

Career statistics Club

International

Scores and results list Republic of Ireland's goals first. Score column indicates score after each O'Sullivan goal.

Honours Glasgow City SWPL: 2013, 2014, 2015 Echo Sportswoman of the Year: 2014 SWPL Players' Player of the Year: 2014 FAI Senior International Player of the Year: 2015, PFA Ireland Senior International Player of the Year: 2018, 2019, 2020 NC Courage Most Valuable Player: 2018, 2019 NWSL Players' Team of the Year: 2019 The Irish Times/Sport Ireland Sportswoman of Month: November 2019 W-League Player of the Month: December 2019 NWSL Best XI Second Team: 2023 Echo Sportswoman of the Month: July 2024 Ireland Women's Supporters Club Player of the Year: 2024-25