Nicoletta Mantovani filed the lawsuit last month after warning that speculation about the state of her marriage to Pavarotti would not be tolerated, her lawyer said.
Pavarotti died Sept. 6 of pancreatic cancer at age 71. Soon after, friends close to the tenor told Italian media that he had been unhappy in the marriage, and that Mantovani was fighting his grown daughters from an earlier marriage over his estate.
"Since the comments did not cease and were, in fact, reiterated Mantovani had no choice but to file the lawsuit," lawyer Anna Maria Bernini said, confirming weekend reports in the small daily L'Informazione, based in Pavarotti's hometown of Modena.
"She is doing it to protect her sense of respectability privately for the sake of her daughter and the memory of the maestro, publicly for her image and any future professional activity," Bernini said.
Mantovani had a daughter with Pavarotti: Alice, who is 4. The tenor also had three daughters from his first marriage.
The two people named in the lawsuit are longtime Pavarotti friends Franca Corfini Strata, wife of the singer's dietician, and Lidia La Marca, wife of conductor Leone Magiera, who often performed with Pavarotti.
Mantovani is seeking Ђ15 million (US$22 million) in damages from each woman, Bernini said. She said Mantovani intends to donate any award to charity. No hearing date has been set.
Corfini Strata had no comment, her husband's office said. La Marca was not available for comment, her office said.
In a newspaper interview following Pavarotti's death, La Marca was quoted as saying the tenor had complained that Mantovani was isolating him and was only thinking about money.
"'Over the last years, Nicoletta has been tormenting me; she makes me live alone,"' La Marca quoted Pavarotti as saying from his hospital bed on Aug. 16, La Stampa said.
"'She's constantly thinking about money, she comes over with documents I'm supposed to sign. She threatens not to let me see Alice anymore,"' she quoted Pavarotti as saying.
Both women named in the lawsuit appeared on a popular show on public RAI television, Porta a Porta, and confirmed their accusations about Mantovani.
Last month, Mantovani took to the airwaves herself, saying she felt compelled to set the record straight.
Pavarotti was one of the biggest opera stars of the late 20th century, winning over audiences with his showmanship and powerful voice.