American singer/songwriter Taylor Swift is insanely happy and smitten by boyfriend, Scottish singer/DJ Calvin Harris.

The 25-year-old Red singer, who once predicted she will be single when she turns 30, has started believing in true love after meeting the 31-year-old DJ.

"Calvin has Taylor believing in fairytales again. She had gotten to a place in life where she'd given up on fairytales and Prince Charming, but Calvin came along and swept her off her feet. It was a total surprise — she never expected this," a source told Hollywood Life.

Reports that Harris and Swift are dating started in March, and the two were pictured shopping in Nashville, dressed similarly.

Later, the two were spotted at a Kenny Chesney concert, getting cosy in the audience.

The couple made their relationship public when Swift kissed Harris during the Billboard Music Awards 2015, held at the MGM Grand Arena in Las Vegas on 17 May.

"She's got all these ideas for happy love songs now because of him. Even though she hates saying goodbye, spending time apart is making it really exciting," another insider said. "When they do see each other the tension is so built up, it's total fireworks and she's putting that passion into her new songs."

"Taylor would love to marry Calvin she already talked about how she would take his name for her personal life but she'll always stay 'Taylor Swift.' Taylor doesn't think it's a sure thing, she's not that cocky, but she has a really good feeling that they will end up together. Even though they haven't been together that long if he did ask her tomorrow she'd say yes, she's just so happy with him," the source added.

It was previously revealed that the Bad Blood singer has been single since splitting up with One Direction singer Harry Styles, after the pair dated for a whirlwind two months in 2014.

Swift has a history of dating high-profile celebrities and has previously been linked with Jake Gyllenhaal, Joe Jonas, Taylor Lautner, John Mayer, Zac Efron and Conor Kennedy.