Minaj is one of the headliners of the festival, along with Liam Payne, Steve Aoki and R3 Wire & Varski.
The letter criticizes Crown Prince Mohammed bin Salman, who financed the event.
Any woman attending will need to obtain permission from a man and must be accompanied to attend.
“You recently celebrated Pride Week to stand in solidarity with the LGBTQ community. Yet, if you move forward with this performance, you will be condoning, and serving the public relations needs, of a government that executes homosexuals for the “crime” of being who they are. It would be disastrous for a public figure of your standing who has articulated a commitment to education, women’s rights, and social justice.”