[4] Murray made his competitive debut for Munster against Connacht in the Celtic League on 18 April 2010, coming on as a blood replacement.

[5] He part of the Munster A team that lost the final of the 2009–10 British and Irish Cup to Cornish Pirates on 16 May 2010.

[6] Murray came off the bench to replace Duncan Williams during Munster's historic 15–6 victory against Australia on 16 November 2010.

[8] On 28 May 2011, he started at scrum-half against Leinster in the 2011 Celtic League Grand Final, which Munster won 19–9 in Thomond Park.

[9] In his first full season with Munster, Murray won the John McCarthy Award for Academy Player of the Year.

[11][12] He won the Man-of-the-Match award for Munster in their Heineken Cup round 4 match against Scarlets on 18 December 2011.

[13] Murray made his comeback from the knee injury he suffered in the 2012 Six Nations in the Heineken Cup quarter-final against Ulster on 8 April 2012.

[14][15] He scored his first try for Munster in the United Rugby Championship league fixture against Glasgow Warriors on 14 April 2012.

[22] Murray started for Munster against Edinburgh in their opening round 29–23 defeat in the 2013–14 Heineken Cup on 12 October 2013.

[36] Murray started in Munster's first European Rugby Champions Cup game against Sale Sharks on 18 October 2014, scoring a try.

[37] He started against Saracens in round 2 of the Champions Cup on 24 October 2014, earning the Man-of-the-Match award in the 14–3 win for Munster.

[43] Murray started the opening pool game of the 2015–16 European Rugby Champions Cup against Benetton on 14 November 2015.

[52] Murray scored Munster's first try in their 20–19 win against Toulon in the quarter-finals of the 2017–18 European Rugby Champions Cup on 31 March 2018.

[56] Having missed the opening stages on the 2018–19 season due to a neck injury, including the 2018 Autumn Tests, Murray made his return from injury during Munster's Pro14 round 9 fixture against Italian side Zebre, featuring off the bench and replacing Neil Cronin in the second half of the provinces 32–7 away win.

[58] Murray earned his 150th cap for Munster in their 24–20 home defeat against provincial rivals Connacht in round 3 of the Pro14 Rainbow Cup on 14 May 2021.

[59] He signed a contract extension with Munster and the IRFU in December 2021, a deal that will see Murray remain with his home province until at least July 2024.

[65] Murray's first start, and third cap, came against the United States in Ireland's opening Pool C match of the 2011 Rugby World Cup.

[75] Murray continued in the number 9 jersey for Ireland's opening 2012 Autumn Series test against South Africa on 10 November 2012.

Murray was nominated for the 2016 6 Nations Player of the Tournament award, alongside Ireland teammate Johnny Sexton.

[126] Following his performances in the tournament, Murray was nominated for the 2017 RBS 6 Nations Player of the Championship award, alongside teammate CJ Stander.

During the World Cup itself, O'Mahony started in Ireland's opening 27–3 win against Scotland,[145] their shock 19–12 defeat against hosts Japan,[146] the 47–5 win against Samoa in their final pool game,[147] and in the comprehensive 46–14 defeat against New Zealand in the quarter-finals, which brought an end to Ireland's 2019 World Cup.

[148] Retained by new head coach Andy Farrell in his squad for the 2020 Six Nations Championship, Murray started in Ireland's 19–12 opening win against Scotland on 1 February 2020,[149] and in their 24–14 win against defending champions Wales on 8 February,[150] and their 24–12 defeat against England,[151] before the tournament was suspended due to the COVID-19 pandemic.

[154] With the usual format of end-of-year international tests not possible due to the COVID-19 pandemic, Ireland instead participated in the Autumn Nations Cup.

[177] After Jamison Gibson-Park pulled out before kick-off due to injury, Murray was promoted to the starting XV for Ireland's opening fixture of the 2023 Six Nations Championship against Wales on 4 February, being replaced by Munster teammate Craig Casey during the second half of Ireland's 34–10 away win.

[178] With Gibson-Park also ruled out of the round two fixture at home to France on 11 February, Murray retained his place in Ireland's starting XV.

[191] Murray was selected as one of three scrum-halves in the squad for 2013 British & Irish Lions tour to Australia, named on 30 April 2013.

[200] On 10 June 2017, Murray made his first appearance and start for the Lions on the tour, doing so in the match against the Crusaders in AMI Stadium.

[201][202] On 17 June, Murray made his second appearance of the tour, starting in the Lions record 32–10 victory against the Māori All Blacks in Rotorua International Stadium.

[219] The victory made Murray one of only ten players to have won a Lions test match against all three of Australia, New Zealand and South Africa.

[220] Murray was restored to the starting XV ahead of the second test,[221] which South Africa won 27–9 on 31 July to take the series to a deciding third test,[222] for which head coach Gatland again selected Ali Price to start,[223] with Murray coming on as a replacement in South Africa's tense 19–16 win, which secured a 2–1 series victory for the Springboks.