Can Trump Change the Name of the Gulf of Mexico?

President-elect Donald J. Trump said Tuesday that he planned to change the name of the Gulf of Mexico to the “Gulf of America,” one of several foreign policy proposals that left world leaders reeling.

“It has a beautiful ring,” he said of the proposed name change for the body of water that borders several U.S. and Mexican states.

Mr. Trump’s proposal was met with derision in Mexico and glee by late-night comedians, although supporters such as Representative Marjorie Taylor Greene, Republican of Georgia, vowed to make it a reality.

Who named the Gulf of Mexico?

The gulf’s name first appeared on maps used by Spanish explorers in the 16th century, well before the founding of the United States.

On Wednesday, President Claudia Sheinbaum of Mexico displayed a map from 1607 that included the Gulf of Mexico. It also labeled North America as “Mexican America.”

“Why don’t we call it Mexican America? It sounds pretty, no?” Ms. Sheinbaum said.

Can Trump rename the Gulf?

Mr. Trump, as president, could press for changes to geographical names as they are used in the United States.

There is a precedent: In 2015, President Obama used his executive powers to change the name of an Alaska mountain from “McKinley” to “Denali.” Mr. Trump has vowed to reverse that decision.

But whether other countries would honor any change is a different story.

“Today, there is no formal international agreement or protocol in place for naming maritime areas,” said John Nyberg, the director of the International Hydrographic Organization, which works to standardize and chart marine boundaries, in an email.

The national geographic naming authority of the U.S. is the U.S. Board on Geographic Names, he added.

The U.S. Board on Geographic Names, part of the United States Geological Survey, says on its website that it only considers name changes for “compelling” reasons. “Generally,” it adds, “the most important policy regarding names is local use and acceptance.”

What other bodies of water have disputed names?

The body of water that separates Iran from Saudi Arabia has long been a source of tension. Iran wants it called the “Persian Gulf,” while Saudi Arabia prefers “Arabian Gulf.”

The U.S. Navy has used the term “Arabian Gulf,” to avoid friction with an important ally, but the U.S. Board on Geographic Names has mandated use of the “Persian Gulf” for official business.

Contention also exists around the name of the sea that is bordered by Japan, North Korea, South Korea and Russia. Japan refers to it as the Sea of Japan while South Korea maintains that it has been called the East Sea for centuries.

The body of water that borders Brunei, China, Malaysia, the Philippines, Taiwan and Vietnam — commonly known as the South China Sea in the English-speaking world — is also disputed. Different countries have proposed their own names for the sea to highlight their own territorial claims to certain islands.

Emiliano Rodríguez Mega contributed reporting.