This is the fourth year in a row that Swift has taken home the accolade and her eighth American Music Award overall.
The singer thanked her fans, saying that she will always be amazed by their dedication to her.
"Thank you so much," Swift said. "Oh my gosh, this is amazing. I want to thank my band and my crew... and the fans for filling up stadiums and arenas and coming to see us play."
She concluded: "To the fans, you just continue to amaze me. Thank you so much. This is wonderful!"
Swift has also been nominated for Artist of the Year' and 'Favourite Country Album' at tonight's (November 20) ceremony.
In October, she revealed that she has so far written 25 songs for the follow-up to 2010's Speak Now.
The 2011 American Music Awards continue on ABC and will air in the UK on November 26 at 10pm on VIVA.
More from the American Music Awards 2011:
> Enrique Iglesias performs with high school choir at American Music Awards 2011
> Nicki Minaj wins first American Music Award
> Justin Bieber performs 'Mistletoe' at American Music Awards 2011
> Nicki Minaj, David Guetta take the stage at American Music Awards 2011
> American Music Awards 2011: Full list of winners as they are announced