Niall Horan scooped the Best New Artist Award at the star-studded American Music Awards ceremony in Los Angeles on Sunday night and also performed his hit track, Slow Hands.
The 24-year-old star, who hails from Mullingar, said it was "unbelievable" to pick up the coveted award after a "hell of a year".
Horan, whose debut album Flicker hit the top spot both here and in the US triumphed over fellow contenders James Arthur, Julia Michaels, Post Malone and Rae Sremmurd.
Also picking up awards where Bruno Mars who won Favourite Artist and Coldplay who won Tour of the Year.
Pink and Kelly Clarkson opened the ceremony with a cover of R.E.M.'s Everybody Hurts, before host and Black-ish actress Tracee Ellis Ross said the nominations reflect a year of music in the US.
"A year where brave women have started a movement as we own our experiences, our bodies and our lives. You heard me?" she added.
Her mother, Diana Ross, was handed a handed a lifetime achievement accolade and closed the show at the Microsoft Theatre with a medley of her hits I'm Coming Out and Take Me Higher.
"I really, really love being here and I feel so humbled by this," she said.
In a recorded message sitting alongside her husband and former president Barack Obama, Michelle Obama celebrated Ross for reaching "folks of every race, background and walk of life".
Imagine Dragons won favourite pop or rock group, and singer Dan Reynolds said the US had faced too many divisions in the past year.
"This is the country I know, which is of powerful women, talking about our women, talking about empowering our LGBTQ youth," he added.
Lady Gaga performed from her show in Washington DC and was presented with Favourite Female Pop or Rock Artist.
"You just remember, that if you feel different, or you feel not understood, don't you dare give up on who you are - you fight like hell for what you believe in," she told her fans.
No women were selected for top categories including artist of the year, video of the year or tour of the year.
Organisers said the nominations are based on music sales, radio play, streaming figures as well as interactions on social media and tours.
Halsey criticised the gender balance as a "missed opportunity", adding she was "really disappointed to hear near exclusively male names".
She received two nominations for her collaboration with The Chainsmokers on Closer but was not up for a solo award despite having a number one album in the US this year.
Here is a full list of the winners at the American Music Awards:
1. Lifetime achievement - Diana Ross
2. Artist of the year - Bruno Mars
3. New artist of the year - Niall Horan
4. Collaboration of the year - Despacito by Luis Fonsi and featuring Daddy Yankee and Justin Bieber
5. Tour of the year - Coldplay
6. Video of the year - That's What I Like by Bruno Mars
7. Pop/rock male artist - Bruno Mars
8. Pop/rock female artist - Lady Gaga
9. Pop/rock duo or group - Imagine Dragons
10. Pop/rock album - 24K Magic by Bruno Mars
11. Pop/rock song - Despacito by Luis Fonsi and featuring Daddy Yankee and Justin Bieber
12. Country male artist - Keith Urban
13. Country female artist - Carrie Underwood
14. Country duo or group - Little Big Town
15. Country album - Ripcord by Keith Urban
16. Country song - Blue Ain't Your Colour by Keith Urban
17. Rap/hip-hop artist - Drake
18. Rap/hip-hop album - DAMN. by Kendrick Lamar
19. Rap/hip-hop song - I'm The One by DJ Khaled featuring Justin Bieber, Quavo, Chance The Rapper and Lil Wayne
20. Soul/R&B male artist - Bruno Mars
21. Soul/R&B female artist - Beyonce
22. Soul/R&B album - 24K Magic by Bruno Mars
23. Soul/R&B song - That's What I Like by Bruno Mars
24. Alternative rock artist - Linkin Park
25. Adult contemporary artist - Shawn Mendes
26. Latin artist - Shakira
27. Contemporary inspirational artist - Lauren Daigle
28. Electronic dance music artist - The Chainsmokers
29. Soundtrack - Moana