Hatice Cengiz, a Turkish citizen, tweeted that the “heinous murder does not have a statue of limitations”.
Khashoggi, a critic of the Saudi government, was killed inside the Saudi consulate in Istanbul, Turkey, in 2018.
Saudi officials say this was a “rogue operation” not sanctioned by the state. This account has been doubted globally.
Among those questioning the official Saudi line were some intelligence agencies and the United Nations.
Khashoggi had been writing for the Washington Post newspaper and living in the US before his death.
After offering changing accounts of his disappearance, Saudi authorities eventually admitted he was killed in a botched operation by a team tasked with getting him to return to the country.
In December 2019, a court sentenced five unnamed men to death for their role in his killing after a secretive trial in Riyadh.
A UN special rapporteur, Agnes Callamard, labelled the Saudi trial the “antithesis of justice” and urged an independent investigation.
On Friday, Hatice Cengiz wrote on Twitter that Jamal Khashoggi had become “an international symbol bigger than any of us, admired and loved.”
Ms Cengiz added that “Jamal was killed inside his country’s consulate while getting the docs to complete our marriage. The killers came from Saudi with premeditation to lure, ambush [and] kill him.”