Final answer:
Tchaikovsky's wealthy benefactress was Nadezhda von Meck, a Russian businesswoman and patroness of the arts.
Step-by-step explanation:
Tchaikovsky's wealthy benefactress was Nadezhda von Meck. She was a Russian businesswoman and patroness of the arts who provided financial support to Tchaikovsky for over a decade. Von Meck admired Tchaikovsky's music and they maintained a correspondence, but they never actually met in person.