Amnesty International has accused online tourism giants Airbnb, Booking.com, Expedia and TripAdvisor of profiting from "war crimes" by offering services in Israeli settlements.
Amnesty's "Destination: Occupation" study calls on the companies to stop listing tourist accommodation, activities and attractions in settlements in occupied territories.
"They are doing so despite knowing that Israel's occupation of the West Bank, including East Jerusalem, is governed by international humanitarian law under which Israeli settlements are deemed illegal," said the report.
"In doing business with settlements, all four companies are contributing to, and profiting from, the maintenance, development and expansion of illegal settlements, which amount to war crimes under international criminal law."
The rights group accused the firms of "normalising" settlements in the West Bank and East Jerusalem.
"All four companies claim to operate under high ethical values and respect for the rule of law. However, none of these standards appears to influence the companies' decisions in relation to settlement listings," the report says.
"To boost bookings, many listings in settlements boast of their proximity to areas of natural beauty in the occupied territories, such as the Dead Sea, nature reserves and the desert," it added.
"By listing and promoting these natural features and nature-based activities and attractions the digital companies are increasing the attractiveness of the listings, securing greater numbers of tourists and ultimately benefiting financially from the illegal exploitation of Palestinian natural resources."
A report by the UN Office of the High Commissioner for Human Rights (OHCHR), published in 2018, noted that tourism activities "ensure the sustainability of residential settlement communities" and "contribute to the profitability of the settlements".
Amnesty launched a campaign in 2017 calling on governments to prevent businesses based in their countries from operating in settlements.
"Governments worldwide must take action to regulate companies or activities over which they have control," it said.