The 23-year-old joined the Scarlets from Pontypridd two seasons ago and has rapidly gained a reputation as being one of the deadliest counter-attackers in the Magners League.
He has made 31 appearances for the Scarlets and scored five tries since making his debut against Edinburgh on 5th January 2007 as a replacement.
"I've really enjoyed my time at the Scarlets," he said. "I love living in Llanelli and things have definitely gone better than I could have hoped for. To be capped in my first full season as a Scarlet is a dream come true."
Stoddart, who won his first Welsh international cap against South Africa last November, was delighted to extend his stay with the Scarlets by signing a new three-year deal.
"Things are looking really good at the moment," he added. "The Scarlets play an attacking brand of rugby which suits me down to the ground. The new stadium is also going up quickly and I'm looking forward to playing on a perfect running surface and hopefully continue my development with the Scarlets."
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