Ten-year-old Melati, who had been at London Zoo since 2012, was mauled by Asim shortly after they were introduced and could not be saved, despite the efforts of staff.
"Their introduction began as predicted, but quickly escalated into a more aggressive interaction", the zoo said.
Asim and Melati were matched through the European Endangered Species Program for Sumatran tigers, which seeks to rescue the cats from near-extinction, the zoo said.
Trained staff eventually managed to secure Asim in a separate paddock in order for vets to safely attend to Melati, but they confirmed that she had died in the attack.
A meeting between two rare Sumatran tigers at London Zoo had a tragic end when the male animal shocked its handlers and killed his prospective mate.
The zoo says 10-year-old Melati died Friday, Feb. 8, 2019 during her first encounter with Asim, a 7-year-old male.
The zoo explained that any introductions involving large cats always run an incredibly high risk, no matter how prepared the keepers may be. During the introduction, Asim overpowered Melati in a fight.More news: Huawei is Open to EU Supervision - says Executive in Speech
More news: US envoy back from North Korea after talks on Trump-Kim summit
More news: Storm Erik close in on Northern Ireland - warnings in place
The Sumatran tiger is classified as critically endangered and is on the International Union for Conservation of Nature's red list of threatened animals. The last of Indonesia's tigers - less than 400 today - are holding on for survival in the remaining patches of forests on the island of Sumatra.
The zoo says keepers intervened with loud noises, flares and alarms but were too late to save Melati.
London Zoo describes Sumatran tigers as the "rarest and smallest subspecies of tigers" in the world, and are native to the Indonesian island of Sumatra. Asim was recently transferred to London from a Danish safari park to serve as a new mate for female resident tiger Melati.
Zookeepers at London Zoo described Asim as a "handsome confident cat who is known for being very affectionate with the ladies", before his arrival in London.
Representatives at ZSL London Zoo did not immediately respond to PEOPLE's request for comment.
It said the focus now is "caring for Asim as we get through this hard event".