Nosipho Regina Shulubane filed an application at the magistrate’s court seeking to block the Saturday marriage, claiming Tsvangirai had promised to marry her.
“We are still very much in love and as such I object to granting of a marriage licence,” Shulubane said in the court papers.
“In February 2011, Morgan proposed and asked me to marry him and he indicated that he wanted to have a wedding ceremony and wed me in Zimbabwe.”
The latest case comes a day after the High Court threw out a bid by Locardia Karimatsenga Tembo, a former lover of the 60-year-old Tsvangirai, to block his planned wedding to Elizabeth Macheka.
Claiming she was customarily married to the prime minister, Tembo had demanded $15,000 a month in maintenance expenses for her upkeep. She will appeal the ruling.
Tsvangirai’s office dismissed the two cases as part of a campaign to tarnish his image.
“It is evident these are not normal claims,” said the prime minister’s spokesman Luke Tamborinyoka.
“The latest claim, for example, has sought to wrongfully allege that the complainant had engaged with Prime Minister Tsvangirai. This is false.”
Tsvangirai broke up with Tembo in November last year and has since become engaged to Macheka.
Their wedding on Saturday is expected to be attended by regional leaders and senior government officials.
Macheka, 35, is the daughter of a senior member of President Robert Mugabe’s ZANU-PF party.
Tsvangirai, announcing the termination of his relationship with Tembo last year, said the relationship had been “irretrievably damaged” to the point where marriage had become “inconceivable”.
Tsvangirai’s first wife of 31 years, Susan, was killed in a car accident in March 2009, just weeks after he went into a unity government with his long-time rival Mugabe following failed elections in 2008.