Felix Jakens, Amnesty International UK's head of campaigns, called for Joshua to "inform himself of the human rights situation and be prepared to speak out about Saudi Arabia's abysmal human rights record".
"If Anthony Joshua fights Andy Ruiz Jr in Saudi Arabia, it's likely to be yet another opportunity for the Saudi authorities to try to 'sportswash' their severely tarnished image," he added.
"Despite some long-overdue reforms on women's rights, Saudi Arabia is currently in the grip of a sweeping human rights crackdown, with women's rights activists, lawyers and members of the Shia minority community all being targeted.
"There's been no justice over the gruesome murder of Jamal Khashoggi, and the Saudi-led military coalition in Yemen is carrying out indiscriminate attacks on homes, hospitals and market-places with horrific consequences for Yemeni civilians."