Mary-Kate Olsen is dating Seth Campbell?

Mary-Kate Olsen is dating a shoe designer. The 24-year-old actress-and-fashion designer — who split from artist Nate Lowman in February 2010 after a two-year relationship — was spotted on a date with Upper Echelon Shoes co-founder Seth Campbell at Lavo restaurant and nightclub in New York.

“Their relationship is fairly new. They’ve been able to have a few dates on the down low. He’s a downtown kind of guy, likes to party every now and then,” a source said.

“His company is in the press but he’s not, so it works out that way. They’re both like each other and are just seeing where things go. Having fun.”

The couple have also enjoyed numerous other dates in New York, including a night out with Mary-Kate’s actress sister Elizabeth at The Jane hotel to celebrate her 22nd birthday.

Before embarking on a relationship with previous boyfriend Nate in 2008, Mary-Kate was linked to a string of men — including the late actor Heath Ledger — but had been officially single since 2005 when she split from Greek shipping heir Stavros Niarchos.

Mary-Kate shot to fame alongside twin sister Ashley in hit US TV show Full House aged nine months.