Elin Manahan Thomas knocked Katherine Jenkins off the number two spot last week with her album Eternal Light.
The 29-year-old soprano, of Cobham Close, Penyrheol, said it was a dream come true.
She said: "I am very pleased. To have a debut solo disc in the classical chart is more than I could ever have dreamed of.
"It is very exciting. Never in my wildest dreams did I think I'd even get in to the charts, never mind going so far.
"Andrea Bocelli is number one and I'm stunned to be in the same list as him."
The former Ysgol Gyfun Gwyr and Gorseinon College student said she had an ambition to sing at a Scarlets' match.
"I'm a huge Scarlets fan and have been from birth," she said.
"So much so that my husband, Bob Davies, also an opera singer, who was a Whites supporter, has had to convert.
"I would be bowled over to be asked to sing at a match."
The singer has signed a five-album deal with Universal Classics and Jazz - the label of Bryn Terfel, Katherine Jenkins, and Lesley Garrett.
She was first recognised after filming a documentary called Soprano Bach for S4C.
She said: "The right person saw it at the right time. I was invited to sing for Universal and when they offered me a deal you could have knocked me down with a feather."
Since then Elin admits it has been a whirlwind of activity.
She said: "I spent the autumn choosing and practising repertoire, and in November all my dreams came true when I recorded my favourite music with the world's leading baroque orchestra.
When compared to Katherine Jenkins, also a former student at Gorseinon College, Elin said she is flattered.
"If I could have half her success I'd be delighted," she said.
Source: Llanelli Star