Twelve months after she came within a whisker of winning the mile and one eighth (1800 metres) race, Napravnik broke through to win the $1 million event with a superbly judged ride.
"It's unbelievable, I'm just so happy," said Napravnik. "I cried a little but I don't think I'm done crying yet."
Trailing Broadway's Alibi to the home turn, Napravnik made her move approaching the iconic Twin Spires, passing the leader on the outside then riding furiously to the line as the crowd of 112,000 let out a mighty roar.
Believe You Can paid $29.60 for a $2 win bet.
Broadway's Alibi held on for second, three quarters of a length behind the winner, while the favourite Grace Hall came third, a further two and a half lengths adrift.
"Last year was kind of a tease, I was so close but not there," Napravnik said. "This year I was determined to be the one in the winner's circle and I had the right horse to do it."
Napravnik, 24, has already left her mark on the male-dominated sport since getting her jockey's license in 2005.
Two years ago, she became the first woman to win the riding title at Delaware Park. Last season took the Fair Grounds riding title and won the $1 million Louisiana Derby with Pants On Fire.
Napravnik finished ninth in the 2011 Kentucky Derby with Pants On Fire - the best finish in the race for a female jockey - but missed out on a ride this year after her mount Mark Valeski was scratched.
"I think the whole female versus male issue just comes down to talent," she said. "If you're talented it's not going to matter what sex you are."