Alexandra Tremontaine was a Human ambassador who worked with the Federation's Bureau of Interplanetary Affairs in the late 23rd century. She was born in the city of Montréal, Québec, Earth, in an area known as Plateau Mont-Royal.

Prior to the 2290s, Tremontaine had built up an impressive career over more than twenty-five years as a mediator and an ambassador. Among her many achievements was ending the long war on Epsilon Canaris III, convincing the Gorn Hegemony to establish a long-term ceasefire with the Federation, and establishing programs on many non-aligned planets that allowed medical aid to be supplied.

In 2293, Tremontaine traveled from Earth to Orelte to aid Spock in negotiating rubindium mining rights with the Frunalian ambassador, Jalira Tren. Upon her arrival at the meetings twenty-seven minutes late, she decided to announce that the Federation were ready to pull-out of the negotiations. While Spock didn't agree with her outright lie, the ends did justify the means as several days later Tren agreed to the terms that had been laid out.

Following the completetion of the negotiations on Orelte, Tremontaine traveled to Marcos XII for an unspecified diplomatic occassion. Following the completion of this mission, she traveled to Alonis to aid Spock in his negotiations with the Alonis on the placement of a starbase on the planet. (TOS novel: Crucible: The Fire and the Rose).