Taylor Swift joined Hayley Kiyoko on stage for a "Delicate" duet. (Screenshot/Twitter)

Taylor Swift has joined Hayley Kiyoko in a surprise performance at a benefit concert in support of LGBT+ youth in New York.

Kiyoko was billed to perform at The Ally Coalition Talent Show at Town Hall New York on Wednesday along with other artists such as Lana Del Rey and Regina Spektor.

The charity event is organised by musician and music producer Jack Antonoff, who founded The Ally Coalition in 2012 to advocate for LGBT+ equality and inclusion, and his sister, fashion designer Rachel Antonoff.

“Hayley is killing it.”

— Taylor Swift

Swift, who has often worked with Antonoff on her albums, performed her Reputation hit “Delicate” in a touching duet with Kiyoko, to close the “Feelings” singer’s set.

“So I’m gonna bring out a friend, she’s really talented, she just got off tour, she just signed with Universal, and she’s really nervous,” Kiyoko said introducing Swift to the show, Variety reported.

“It’s so great to be at this incredible show,” Swift said, complimenting Kiyoko on her performance.

“Hayley is killing it,” she said, adding: “Her family’s in the audience, so Haley’s killing it, RIGHT?”

Taylor Swift and Hayley Kiyoko have performed together before

Swift has long been supportive of Kiyoko, bringing her out to perform “Curious” together at the 66,000-capacity Gillette Stadium in Massachusetts in July—Kiyoko’s first stadium performance.

In April, Swift also defended Kiyoko after the openly lesbian singer, nicknamed by her fans as “Lesbian Jesus,” denounced homophobia in the music industry.

Taylor Swift and Hayley Kiyoko thrilled their fans in July (hayleykiyokoBR2/twitter)

Kiyoko said she faced resistance for doing several music videos about girls, citing Swift as an example of double standards in the industry.

“I’ve had several music industry execs say, ‘You’re doing another music video about girls?’” Kiyoko said in an interview with Refinery29. “I literally looked at them and was like, um, yea …Taylor Swift sings about men in every single song and video, and no one complains that she’s unoriginal.”

Swift told her fans it was Kiyoko’s right “to call out anyone who has double standards about gay vs straight love interests.”

She wrote: “We should applaud artists who are brave enough to tell their honest romantic narrative through their art, and the fact is that I’ve never encountered homophobia and she has.”

Taylor Swift’s increasingly vocal support of LGBT+ rights

Swift, who had faced criticism for her long-standing silence on political issues, has recently become more vocal in her support of women’s and LGBT+ rights.

In June, she made an emotional speech in support of her LGBT+ fans at the start of Pride month and, a month ahead of the US midterm elections, she publicly endorsed Democrat political candidates for the first time.

Taylor Swift has become an increasingly vocal supporter of LGBT+ rights. (Christopher Polk/Getty)

Swift announced she would be voting in the state of Tennessee and came out against Republican candidate Marsha Blackburn, citing her voting record against women’s rights and LGBT+ rights as reasons for her opposition.

“I believe in the fight for LGBTQ rights, and that any form of discrimination based on sexual orientation or gender is WRONG. I believe that the systemic racism we still see in this country towards people of colour is terrifying, sickening and prevalent,” she wrote in an Instagram post to her 112 million followers.

“I cannot vote for someone who will not be willing to fight for dignity for ALL Americans, no matter their skin colour, gender or who they love,” Swift added.

Blackburn ended up winning her Senate seat, but US voter registration among people aged 18 to 29 spiked after Swift’s message.

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