Lady Gaga kicked off the city’s 2019 WorldPride weekend with a surprise appearance outside the historic Stonewall Inn in Greenwich Village on Friday in honor of the 50th anniversary of the 1969 riots.

The “Born This Way” singer strutted onto a stage near the historic venue with thigh-high rainbow boots and a Versace jacket to sing for a throng of supporters enjoying a weekend of LGBT Pride events — which culminates with the march on Sunday.

“It used to be unheard of to even come out of the closet,” the Manhattan-born singer said before noting the progress that has been made. “This is your freedom!”

Gaga, who is bisexual, has long been a supporter of LGBT issues.

“This community has fought and continues to fight a war of acceptance, a war of tolerance and the most relentless bravery,” she bellowed. “You are the definition of courage. Do you know that?”

Gaga then grew emotional behind her black sunglasses.

“I really, really hope you celebrate every inch of who you are today,” she told the roaring crowd made up of men, women and trans people of all ages. “You were born this way. And you are superstars.”

The “Star is Born” actress also pledged her devotion to the LGBT community.

The massive swell of supporters, some waving tiny rainbow flags and others waving Pride folding fans, fell silent as Alicia Keys performed Cyndi Lauper’s classic “True Colors.”

“We want equality. We want to be free,” Keys said on stage.

She wrapped up her short set with “Empire State of Mind.”

“I love you,” Keys told the crowd. “We’re in this together. May we continue to fight for tolerance.”

The two-hour, star-studded event — which included appearances by Chelsea Clinton, Donatella Versace and Whoopi Goldberg — launched a weekend of Pride events in the city.

Sunday’s march steps off at Fifth Avenue and 26th Street at noon, when millions of people are expected to take part in the largest Pride celebration in the world.

The march will make its way south into the Village past the Stonewall National Monument, then up Seventh Avenue past the NYC AIDS Memorial Park.

Organizers have said that more than 4.5 million spectators will watch the parade this year — nearly double the

2½ million in attendance last year. The number of people marching in the parade is expected to be 150,000, about 67,000 more than last year.