Belgium's royal family says it has contacted the fast food chain Burger King over an ad that invites people to choose between the country's King Philippe and the company's mascot.
The ad, on whoistheking.be, asks those who choose Philippe: "Are you sure? He won't be the one to cook your fries."
A spokesman said the use of the king's image must be approved by the royal family, but they had not been asked.
On the website, Philippe is represented by a cartoon.
"We disapprove of this approach," royal spokesman Pierre Emmanuel de Bauw said.
"Since it is for commercial purposes, we would not have given our authorisation."
On the ad website, if a user chooses Burger King no more prompts appear. If they choose Philippe, they get asked twice whether they are sure - and the second time, the only option is "no".
Votes are open until 19 June. The chain will open its first outlet in Belgium at the end of June.
A Burger King representative told the news agency EFE it had not received any communication from the monarchy.