The 23-year-old defender drilled home the only goal of the final in Sydney on Sunday to help La Roja win the World Cup for the first time in their history.
"And without knowing it, I had my Star before the game started," she posted on X, formerly Twitter.
"I know that you have given me the strength to achieve something unique. I know that you have been watching me tonight and that you are proud of me.
"Rest in peace, dad."
The Spanish federation (RFEF) said Carmona "learned the sad news after the World Cup final."
"We send our most sincere embraces to Olga and her family in a moment of deep pain. We love you, Olga, you are in the history of Spanish football," it added.
The Real Madrid star dedicated her goal to the late mother of one of her best friends, displaying an undershirt with "Merchi" written on it when she scored.
"I want to say this victory is for one of my best friend's mother, who died recently. I celebrated the goal with that shirt," Carmona told Spanish state broadcasters La 1, soon after the game's conclusion.
Carmona's club Real Madrid said it "wants to express its condolences and affection to Olga, her relatives and all her loved ones" in a statement.
"Rest in peace."
The final
The gripping Women's World Cup encounter was a fitting conclusion to a tournament in Australia and New Zealand which has broken records and will be remembered for how the supposed minnows closed the gap on the sides at the top.
In front of a packed crowd of nearly 76,000 at Stadium Australia in Sydney, Spain were the more accomplished side and had more chances, including missing a second-half penalty.
Spain's triumph was vindication for Jorge Vilda and the Spanish football federation, who stuck with the coach even after 15 players last year said they no longer wanted to represent their country under him.
Defender Carmona scored what turned out to be the winner, rampaging from left-back to thrash the ball in low and hard on 29 minutes past England goalkeeper Mary Earps.
"It's difficult to describe, immense joy, I'm so proud of this team," said the 42-year-old Vilda, who was accused of being too strict, among a litany of complaints.
Minnows make mark
Women's football still faces a battle for equality with the men's game and several teams at the World Cup were in open dispute with their federations over pay and conditions.
Off the pitch, the biggest Women's World Cup in history, with 32 teams, was the best-attended ever and most games were played in front of bumper crowds.
On it, a tournament full of surprises signalled the end of the United States' long reign as the superpower of women's football as their dreams of an unprecedented third title in a row came to an end in the last 16, their earliest exit ever.
Sweden, who dumped out the Americans on penalties, finished third after beating Australia 2-0 on Saturday.
The Matildas had the consolation of capturing the hearts of the home nation, their exploits in reaching the semi-finals for the first time splashed across the front and back pages of local newspapers on an almost daily basis.
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