The 27-year-old, who has signed a three-year deal, scored 41 times in 110 appearances since arriving from Rotherham for B£300,000 three years ago and he has netted 15 times this season despite not always being first choice.
Le Fondre's arrival comes less than 24 hours after the Bluebirds announced that fellow forward Federico Macheda had signed a three-year deal and will join when his Manchester United contract expires on July 1.
Le Fondre said: "It's such a great opportunity for me to come here to Cardiff City and play for a boyhood hero of mine in Ole Gunnar Solskjaer, it was a move I just couldn't say no to.
"I'm delighted to be working with Ole and I can't wait to get started. Scoring is what I'm about, I've often got into double figures during my career, although looking back at last season it's one I really wanted to score more in personally.
"They are the high standards I set myself and now the aim is to do that with Cardiff City."
He added on Twitter:
"Delighted to announce I've signed for @CardiffCityFC Looking forward to bouncing straight back to premier league with them!!"
- Sports & Recreation
- Le Fondre
- Cardiff City
- Ole Gunnar Solskjaer
- Federico Macheda