Starting today, US citizens will no longer be required to tick male or female in their passport applications.
Applicants will now be able to express themselves as "X", apart from male or female options.
Biden administration aims to protect Americans against some state laws against transgender people with third option decision
Activists see the new app as a landmark.
US Secretary of State Antony Blinken, said that the option to mark gender as X will be valid for other documents besides passports next year.
Until last year in the country, those who wanted to reflect the gender change in their passport had to get a document from the doctor first.
In October, after a long legal struggle, for the first time in the state of Colorado, a passport was issued to a person, in which the gender part was expressed as "X".
Now, a new era will begin for the more than 1 million Americans who see themselves as transgender or outside the existing binary gender classification.
In the USA, the Biden administration reacted to the Republican governors of Oklahoma and Arizona signing the bills that prohibit the participation of trans athletes in sports for girls in schools.
"Every American has the right to be himself," the White House said in a statement. However, many trans-Americans still face systematic barriers, discrimination and acts of violence.