Billboard confirmed the duo's achievement on Twitter, writing: "@samsmith and @kimpetras are the first publicly non-binary and transgender artists, respectively, to earn a No. 1 song on the #Hot100, thanks to 'Unholy.'"
The bold song about an illicit affair soared to the top of the charts following its release last month. The accompanying music video has had more than 29 million YouTube views.
While Smith has had eight UK number ones, including their Grammy award-winning song "Stay with Me," this is British singer's first on the Billboard Hot 100.
Petras, a transgender woman, shared the news on her Instagram page, telling her 775,000 followers that she was "so grateful" for the song's success.
"Sam, I can't thank you enough for riding with me for years at this point," the German pop star wrote. "I'm so honored to be part of your first number one in the US which you should have 500 of at this point. I love you forever angel Sam."
Smith told fans on Instagram that they were "speechless, overwhelmed, nautious and extremely happy" after getting their first US number 1.
The 30-year-old musician added: "I am so honored to get to work with such incredibly talented musicians and humans. And Kim... what magic you are. You are a treasure and an inspiration to so many. Thank you for jumping with me."
"Unholy" is the second single from Smith's fourth studio album, "Gloria," which is set for release in January.
Smith's last album was 2020's "Love Goes," which spawned hits including "Dancing with a Stranger" and "Diamonds."
Petras, 30, released her debut single "I Don't Want It at All" in 2017 and her most recent project was the EP "Slut Pop," which she unveiled in February.
In 2019, she told UK outlet Metro that while she is a transgender activist, she wants her talent, not her gender, to be the topic of conversation.
"I want to be taken seriously," she said, adding that she wants to "just be like any other artist, to be judged on the quality of my music, and not on my gender."
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