Published Friday, 31 August 2012
Firth celebrates the win. (© Getty)
The Seaford 15-year-old triumphed in the S14 100m backstroke final on Friday.
She finished in a time of 1:08.93 ahead of Australia's Taylor Corry, who took silver, and bronze medallist Marlou van der Kulk of the Netherlands.
It means she has clinched Ireland's first gold of the Games in London.
"It's amazing," she said. "I'm over the moon, I can't believe it.
"Words can't describe how I feel at the minute. I thought I came third and I was like 'oh, okay' and then I saw first and I was like 'oh, my word'.
"I had a shoulder injury going into it and stuff so it sort of set me back.
"I wasn't expecting too much but then to see the gold, everything was worth it at the end. It's so good."
More good news followed as Londonderry sprinter Jason Smyth won his heat in the 100m T13, setting a new World Record as he crossed the line with a time of 10.54s.
Before the competition Smyth, who has been described as the Usain Bolt of the Paralympics, told UTV: "Going in as champion I've got to be confident that it is there for me to win again.
"I don't think anybody that is in this situation going in as favourite or champion of previous that you've got your mind on anything else but winning again."
Earlier in the men's 100m backstroke S9 final, Laurence McGivern of Rostrevor finished eighth in a time of 1:06.11. It was his first time competing in a Paralympics.