He was a goal-kicking loose forward in rugby league, who played for Wigan between 1991 and 2004, winning six Championships and four Challenge Cups, as well as numerous individual awards.

He coached them to a 2–1 series victory in New Zealand in 2022 and two consecutive Six Nations Championships wins in 2023 and 2024, including a Grand Slam in 2023.

[4] Farrell first played rugby league at age 10 at a summer camp run by Graeme West, who was Wigan captain at the time.

Farrell became the youngest player to win a Challenge Cup final in 1993 when at 17 years and 11 months he came on as a substitute against Widnes.

On 28 September 1997 in the 1997 Super League Premiership Final, Farrell played at loose forward in Wigan's 33–20 win over St. Helens at Old Trafford before a crowd of 33,389.

[9] In the 1997 post-season, Farrell was selected to captain Great Britain at stand-off in all three matches of the Super League Test series against Australia.

He captained the Wigan Warriors as a second-row in their 1998 Super League Grand Final victory over Leeds Rhinos.

Farrell played for the Wigan Warriors at loose forward, scoring a try and kicking two goals, in their 2000 Super League Grand Final defeat by St. Helens.

Farrell played for the Wigan Warriors at loose forward in their 2001 Super League Grand Final defeat by the Bradford Bulls.

Farrell played for Wigan Warriors at loose forward and kicked two goals in the 2003 Super League Grand Final defeat by the Bradford Bulls.

[11] He retired while second on the list of the England rugby league side's all-time top goal scorers (behind George Fairbairn), with 78 points.

Farrell made his England début at Twickenham after he was named at inside centre in the first Six Nations game against Scotland.

The 2007 World Cup saw Farrell starting at inside centre against South Africa, in England's chastening group stage defeat.

There were rumours of Farrell returning to rugby league and rejoining Wigan Warriors after it emerged that Saracens head coach Eddie Jones had become unhappy with the direction his club was taking.

After the successful campaign Farrell was given the chance to become a permanent part of the England coaching team, but decided to return to Saracens.

He was heavily praised by head coach Warren Gatland,[citation needed] having drilled the team to concede very few points during the 10-match tour.

[21] On 6 January 2016, it was announced that Farrell would take up the role of Ireland defence coach after the completion of the 2016 Six Nations Championship.

As his previous contract with England prevented him from working with an international team until April 2016, Farrell joined Irish province Munster in January 2016 in a temporary advisor role that was to last for four months.

[41] On 14 December 2023, Farrell signed a new four-year contract to remain as Ireland head coach until the end of the 2027 Rugby World Cup.