The One Direction star, who has been linked to a number of older women, apparently regards the 51-year-old Loose Women host as the "ultimate cougar".
"Harry absolutely fancies the pants off of Carol, and has for years," a source told the Daily Star.
"He has always said that he would love to take her on a date but that he wouldn't have the guts to actually ask her out in case she turned him down.
"But Carol is definitely the ultimate cougar for Harry."
Styles has previously dated The Xtra Factor host Caroline Flack and married DJ Lucy Horobin.
He was also linked to 19-year-old Burberry model Cara Delevingne last week.
Watch One Direction's video for 'What Makes You Beautiful' below: