With more than 96 percent of polling places reporting, Fernandez, a center-left Peronist party candidate, had 45 percent of the vote, nearly twice as much as her closest rival.
Fernandez, a lawyer and senator, four years ago followed her husband to the Pink House, Argentina's presidential palace, drawing comparisons to former first lady Sen. Hillary Clinton, D-N.Y., and Argentina's previous power couple, Juan and Evita Peron.
"We have won amply," Fernandez, 54, said in her victory speech Sunday night. "But this, far from putting us in a position of privilege, puts us instead in a position of greater responsibilities and obligations."
Fernandez's victory has been viewed as a referendum on her husband's presidency, under which Argentina recovered from a 2001 economic crisis and repaid a $9.5 billion debt to the International Monetary Fund. Others, however, have cautioned her against embracing all of Kirchner's policies, as Argentina is suffering from high inflation, an energy crisis and a shrinking budget surplus.
"Her husband had the advantage of everyone saying, 'He got us out of the crisis,'" Michael Shifter of the Inter-American Dialogue told the Associated Press. "Well, they can't say that about her, because they already got out of the crisis."
To become president, Fernandez defeated center-left lawmaker Elisa Carrio, who claimed 23 percent of the votes, and Economy Minister Roberto Lavagna, who garnered 17 percent. Eleven other candidates split the remaining votes.
When she takes office Dec. 10, Fernandez will be Argentina's second female president, but the first through an election. Isabel Peron, who married Juan Peron after Evita's death, was vice president when he died in 1974 and served for nearly two years before a military coup ousted her.
"This is a dynasty-in-waiting," Riordan Roett, director of Western Hemisphere studies at Johns Hopkins University, told the AP. "But it will collapse as they all do if she can't get a team together to differentiate herself from Nestor Kirchner."