Farrelly's inspiration into a professional wrestling career came from watching both British wrestling from ITV's World of Sport and American wrestling from the World Wrestling Federation on Sky One. On the advice of Bret Hart, Farrelly began training in Larry Sharpe's Monster Factory wrestling school in April 2002, alongside Tank Toland, Cliff Compton and Cindy Rogers. Six weeks later he officially debuted as a fan favorite under the name Sheamus O'Shaunessy against Robert Pigeon. It was during this time that he developed the nickname the "Irish Curse" after low-blowing an opponent. He soon suffered a serious neck injury after botching a hip toss which sidetracked his career for two years.
Farrelly soon developed his wrestling character by drawing on Celtic mythology. Wanting to move away from limiting Irish stereotypes of lucky charms, leprechauns and alcoholism, he instead wanted to portray an Irish warrior. Going to a Gaelscoil, Farelly grew up aware of the four cycles of Irish mythology and, inspired by the artwork of Jim Fitzpatrick, incorporated the sword and axe-wielding imagery into his gimmick. This included the design of his own pendant, the crossos, which combines the Celtic cross with a Celtic War sword to illustrate his character's "indigenous origins with a hybrid of warrior strength matched with a strong ethical centre."
Irish Whip Wrestling (2004–2006)
In May 2004, still using the ring name Sheamus O'Shaunessy, Farrelly returned to wrestling at the newly opened Irish Whip Wrestling (IwW) school in Dublin. He then made his debut match for the promotion at their Mount Temple show on July 9 against Mark Burns, who he easily defeated. He went on to win a battle royal the following month.
O'Shaunessy spent the rest of the year engaged in a rivalry with Vid Vain after losing to his tag team partner Joey Cabray the same night as winning the battle royal. On October 22 and 23 they traded wins, leading to O'Shaunessy recruiting help from CJ Summers to help defeat the tag team on October 24. Still O'Shaunessy failed to defeat Vain in singles action the following day. Despite these losses, his impressive showings earned him a place against Alex Shane in a guest match for the Frontier Wrestling Alliance (FWA) British Heavyweight Championship. Despite putting on a strong showing and being close to winning, his friend Red Vinny interfered in the match and cost him the championship.
In March 2005 he avenged this loss by teaming with Raven to defeat Shane and Vinny. This victory was part of a winning streak over the end of March where O'Shaunessy wrestled twice a day on March 24, 25, 26 – including an 11 man Rumble win – and 27 with a standard tag match and a ten-man tag team match. This series of victories, aside from one loss by disqualification to Vain, put him good stead for the one-day tournament held in County Kildare to crown the inaugural IwW International Heavyweight Champion. On March 28, O'Shaunessy put an end to his main rivalries when he defeated Vinny and then Vain in the quarter and semi finals, respectively. He met Darren Burridge in the final match and won to become IwW's first champion, but had to compete again in an evening show in Dublin, defeating Burridge and Vinny once more in a tag match alongside Vain.
O'Shaunessy's first successful title defence came against Burridge the following month but Burridge would not let his grudge rest, continuing to attack O'Shaunessy and finally costing him the title during a match against D'Lo Brown on May 29. O'Shaunessy earned revenge in July by defeating Burridge in a grudge match, though lost to him in an arm wrestling contest the following day. Still, he continued on his quest to regain the title by winning a contendership three way match against Vinny and Red Viper in August setting him up to regain the International Heavyweight Championship in October from Brown in Newcastle upon Tyne in England.
After defending his title against Vampiro and Viper, O'Shaunessy found himself embroiled in a new feud with rising Scottish wrestling star "Thee" Drew Galloway, whom he later admitted was his toughest opponent. On January 28, 2006, he received his first championship match, evolving their rivalry from previous non-title contests. The rivalry quickly took on a patriotic flavour, with Galloway's blue colours of Scotland clashing O'Shaunnesy's green colours of Ireland, mirroring the Old Firm football derby between Glasgow Rangers and Glasgow Celtic, respectively. This football allusion became particularly prominent when the two met again at Verona Football Club once again for the title, though the match changed into a Lumberjack match, the result and champion remained the same.
With Galloway defeated, O'Shaunessy continued to dominate by again defending his title against Vampiro on 17 March. Galloway earned himself a two out of three falls match against the champion the following day, however, which O'Shaunessy won two falls to one; the next day produced the same result in a match O'Shaunessy claimed was his best on the independent circuit. With Galloway briefly answered, O'Shaunessy took on the newcomer Pierre Marcaeu and defeated him in two successive title matches only to find Galloway had earned another shot. With their rivalry intensifying, Galloway's next challenge to O'Shaunnesy was given the stipulation of a Last Man Standing match. O'Shaunessy retained the title, as he also did in June with the same stipulation. Finally, on August 28, O'Shaunessy lost the IwW International Heavyweight Championship in a singles match to Galloway in what would be his last appearance with the promotion.
British promotions (2005–2007)
As well as wrestling in Ireland, O'Shaunessy occasionally travelled to Great Britain to make appearances on the British independent circuit. In April 2006 he was brought into Wales' Celtic Wrestling promotion as a contender for their top title but was defeated by the champion, Chris Recall. Later that year in November, he was employed by London's LDN Wrestling to appear on their Capital TV show where, after quickly defeating William Hill, he gained an LDN Championship match against Tex Benedict which ended with Benedict winning by disqualification and O'Shaunessy attacking him after the match.
During his time overseas he worked for Brian Dixon's All Star Wrestling, which gave him a taste of large audiences that he had not experienced in Ireland, as well as wrestling English veteran Robbie Brookside and other British wrestling luminaries, including Nigel McGuinness and Doug Williams. He also represented the UK in a Battle of the Nations tag team match between the UK and Austria alongside Drew McDonald and The Celtic Warrior in a losing effort against Chris Raaber, Michael Kovac & Robert Ray Kreuzer at the European Wrestlng Association's Night of Gladiators.
As well as making top contender appearances based on his growing reputation, O'Shaunessy also brought with him to Britain his long-standing rivalry with Galloway. He had already wrestled in Galloway's home promotion, British Championship Wrestling (BCW), twice in 2005 losing to Jay Phoenix on the day before Phoenix would lose to Galloway in March, and returning in September to defeat one of BCW's top stars, Wolfgang, via countout. In the middle of their IwW feud the following year, O'Shaunessy went back to Scotland to take part in BCW's Path To Glory tour, defeating Galloway on the first night but conceding a loss the to him next night in May. Though their feud finished in Ireland in August 2006, it continued on across the Irish Sea when the two wrestled for the umbrella promtion Real Quality Wrestling (RQW) the following year. The two first met during April's Taking On The World show which ended in a double countout. The lack of a decision led to a rematch in June, and one of O'Shaunessy's last on the independent circuit, where Galloway picked up the victory in a No Holds Barred match ahead of an RQW Heavyweight Championship match.
World Wrestling Entertainment / WWE (2006-present)
On November 13, 2006, O'Shaunessy appeared on the World Wrestling Entertainment (WWE) show Raw at the Manchester Evening News Arena as part of the security team ejecting D-Generation X from ringside only to later receive a Pedigree from Triple H. The following day he and Galloway had a try out match against each other. The following year in April he received another set of try out matches in Milan and London against Galloway as well as Stu Sanders and WWE talent Jimmy Wang Yang and Monster Factory alumnus Domino. This led to signing a developmental contract for WWE, at which point he relocated to the United States.
Florida Championship Wrestling (2007–2009)
O'Shaunessy debuted for the WWE developmental territory Florida Championship Wrestling (FCW) on October 2 in a double-debut match with a win over Bryan Kelly. While wrestling regularly, he was not part of any long feuds but did wrestle with a number of short-term tag teams alongside Hade Vansen and Jake Hager before teaming with Kafu (and managed by Dave Taylor) in the tournament to crown the inaugural FCW Florida Tag Team Champions. They advanced past the first round after defeating The British Lions ("Thee Superstar" Christopher Gray and "The Rascal" Tommy Taylor) but lost to Brad Allen and Nick Nemeth in the second round.
By September, O'Shaunessy had focused his attention to singles competition and wrestled his way to the top of the card, successfully defeating former partner Hager for the Florida Heavyweight Championship. He defended the title against Hager on October 23 and took on a number of competitors, with Eric Escobar and Joe Hennig consistently earning themselves into contention. Eventually, on December 11, O'Shaunessy lost the title to Escobar in a four-way match also involving Hennig and Drew McIntyre (formerly Drew Galloway).
O'Shaunessy spent 2009 continuing to chase gold, earning two shots over January and February at the Florida Tag Team Champions Johnny Curtis and Tyler Reks but he and Ryback were unsuccessful in both attempts. In March he challenged the two for the titles once again, this time with McIntyre as his partner but could not defeat them, nor could he defeat McIntyre for the Florida Heavyweight Championship the following month. He received a series of chances throughout the rest of the year but could not win any more titles before being called up to WWE television, unsuccessfully challenging Justin Angel for the Florida Heavyweight Championship in November.
On July 22, 2008 O'Shaunessy worked a dark match at a SmackDown taping, losing to R-Truth. The following year in May, O'Shaunessy began appearing at the Raw brand's house shows, and on both May 8 and 9 he defeated Jamie Noble along with another dark match victory over Noble before an episode of Raw.
On the June 30, 2009 episode of ECW, Farrelly made his unannounced debut as a villain under the shortened ring name of Sheamus, quickly defeating a local competitor. Sheamus soon entered into a critically well-received rivalry with Goldust after defeating him on July 29. After exchanging victories in the following weeks the two appeared on the Abraham Washington Show talk segment leading to a No Disqualification match on September 1 which was won by Sheamus. Sheamus then began a feud with Shelton Benjamin which was hot-shot into a deciding match on October 27 which Sheamus won. [[File:King Sheamus 2010 Tribute to the Troops.jpg|thumb|Sheamus as the 2010 King of the Ring.]
Raw, WWE Champion and King of the Ring (2009-2010)
His rivalry with Benjamin ended prematurely because Sheamus had already been moved to the Raw brand. He made his Raw debut by defeating Jamie Noble on October 26. In the following weeks, he continued to attack Noble causing him to retire, and, in lieu of competition, assaulted the timekeeper and commentator Jerry Lawler on November 16 at Madison Square Garden. The following week Sheamus appeared on his first WWE pay-per-view event, Survivor Series. Sheamus appeared as part of The Miz's team in a traditional five-on-five elimination tag team match. He eliminated fellow Irishman Finlay and made the final pinfall to eliminate the opposing captain John Morrison and survive along with The Miz and long-time former rival Drew McIntyre.
The following night on Raw, Sheamus won a "break-through" battle royal for wrestlers who had never won a world championship, to become the number one contender to John Cena's WWE Championship. At the contract signing immediately afterwards, Sheamus put Cena through the table as the Raw guest host Jesse Ventura announced it would be a Tables match. On December 13, at the TLC: Tables, Ladders & Chairs pay-per-view, Sheamus defeated Cena to win the WWE Championship, his first championship in WWE, making him the first Irish-born WWE Champion. The following night on Raw, Sheamus was awarded with the 2009 Breakout Superstar of the Year Slammy Award. He went on to successfully defend the championship against Cena on Raw and Randy Orton at the Royal Rumble in January 2010, with both matches ending in disqualification.
On February 21, Sheamus lost the WWE Championship at the Elimination Chamber pay-per-view in the Elimination Chamber match after he was eliminated by Triple H after a Pedigree, and Cena won the match and the championship. During the match, Sheamus suffered a concussion, and as a result, did not attend Raw the following night. Upon his return, he attacked Triple H for costing him the WWE Championship to set up a match between the two at WrestleMania XXVI, which he lost. At Extreme Rules, after attacking Triple H at the start of the show, Sheamus defeated him in a Street Fight. After a series of kicks to the head to win, he continued to attack Triple H after the match finished resulting in Triple H being written off TV for 10 months.
On June 20, at the Fatal 4-Way pay-per-view, Sheamus won a fatal four-way match, following interference from The Nexus that allowed him to pin John Cena, thus winning the WWE Championship ,and beginning his second World Championship reign. He went on to defeat Cena in a steel cage match to retain the championship at the WWE Money in the Bank pay-per-view, and against Randy Orton at SummerSlam, which ended in disqualification, meaning that Sheamus retained his title. At Night of Champions, Sheamus lost the WWE Championship was pinned by Randy Orton in a Six-Pack Elimination Challenge. Sheamus lost a rematch against Orton for the WWE Championship at Hell in a Cell. At Bragging Rights, Sheamus would participate with Team Raw against Team SmackDown. Sheamus was eliminated with The Big Show in a double countout and Team Raw went on to lose the match. At Survivor Series, he lost to John Morrison.
On November 29, Sheamus defeated Kofi Kingston and John Morrison to become King of the Ring, after receiving a bye through the second round. As King Sheamus, he faced Morrison again at the Tables, Ladders and Chairs PPV for a future WWE Championship match but lost the ladder match. Going into 2011, he continued to lose to Morrison in a mixture of singles and tag team matches, before Triple H returned on February 28 and took revenge for his scripted 10 month injury by putting Sheamus through the announce table.
On March 7, after losing a match against Daniel Bryan, Sheamus challenged him to a rematch with his WWE career on the line against Bryan's United States Championship. He won the match the following week, becoming United States champion. The rematch between Sheamus and Bryan took place on April 3, during the preshow of WrestleMania XXVII, and ended in a draw after interference from the lumberjacks. Sheamus was drafted to the SmackDown brand along with his US Championship in April only to lose it to Raw's Kofi Kingston at Extreme Rules. He would reignited his feud with Randy Orton. On the May 27 edition of SmackDown!, Sheamus won a triple threat match to determine the number one contender for the World Heavyweight Championship and lost to Randy Orton for the title the following week.
Farrelly played the role of Two Ton in the 2008 movie The Escapist, which starred Joseph Fiennes and Brian Cox. He had a small role in the 2006 Irish film, 3 Crosses, and was a Celtic Warrior Zombie in the opening sequence of the 2009 movie Assault of Darkness opposite Vinnie Jones. He appeared on several episodes of the famous Irish sockpuppet, Dustin the Turkey's show Dustin's Daily News where he had a rivalry with Dustin. It ended with Dustin and Sheamus having a "fight", which Dustin won. He also appeared on The Podge and Rodge Show as a leprechaun wrestler, along with IwW alumnus George McFly.
Farrelly was born in Cabra, Dublin, but was raised in North Great George's Street, Dublin. Farrelly's father, Mark, was an amateur bodybuilder. Farrelly speaks fluent Irish, having attended Scoil Caoimhin Primary and Secondary School, a Gaelscoil. He sang in the Palestrina Choir until the age of thirteen, as part of which he appeared on both the Christmas Late Late Show and Live at Three. He played Gaelic football for the Erin's Isle team where he was declared Sportstar of The Month. He also played rugby for the National College of Ireland, where he gained a National Diploma.
Farrelly is a former IT technician. He also worked as security for a nightclub which led to him occasionally working personal security for Bono and Larry Mullen, Jr. of U2 as well as Denise van Outen.