WASHINGTON—The State Department said on Wednesday it was introducing a new rule that will enable Americans to select their gender on their passport without presenting supporting medical documentation.

The change will more easily enable transgender Americans to have passports that match their gender identity, and the State Department described it as a step toward promoting equal rights for lesbian, gay, bisexual and transgender people around the world.

The State Department also said it was taking steps to add a new gender marker for persons who don’t identify as either male or female but as “nonbinary, intersex, and gender nonconforming.” It said the process for doing so was complex.

“We are evaluating the best approach to achieve this goal,” Secretary of State Antony Blinken said in a statement.

Previously, passport applicants were required to present medical documentation if the selected gender didn’t match their other identity documents.

The American Civil Liberties Union, a civil-rights group, said in a statement the new rule was an important step forward.

“Improved access to accurate passports will have such a profound impact on the lives of trans, intersex, and nonbinary folks across the country,” said Arli Christian, an ACLU campaign strategist, adding that more remained to be done to implement the change across federal agencies.

Write to Jessica Donati at jessica.donati@wsj.com