Sam Smith just endorsed 20-year-old Sienna Spiro as one of the biggest stars in music right now, and the moment happened live. The moment also went down at one of the most storied venues in San Francisco.
On Wednesday night, Spiro surprised the crowd at Sam Smith’s To Be Free: San Francisco residency at the historic Castro Theatre, joining them onstage for a stunning duet of Spiro’s breakout hit “Die on This Hill.”
The crowd did not see it coming. The reaction said everything.
Afterward, Smith posted about the moment on Instagram:
“Singing with you is like flying. I’m so touched that you came to bless us all last night at the Castro.”
Spiro replied:
“I would’ve never written this song if I hadn’t grown up listening to you. Thank you so much for having me and always inspiring me. You are the greatest, thank you Sam, I can’t believe this.”
Smith has been even more direct elsewhere, saying:
“Sienna is a true artist with the voice of a generation. The world is at her feet.”
Who Is Sienna Spiro?
If you haven’t heard of Sienna Spiro yet, just give it time.
She is a 20-year-old singer-songwriter from London who started releasing music in 2024 and signed with Capitol Records almost immediately.
She opened for Teddy Swims on the road and quietly built a following before “Die on This Hill” changed everything.
The song, a pop-soul ballad about staying in a toxic relationship, has now crossed 300 million streams on YouTube and Spotify combined.
She performed it on Jimmy Fallon in early January, and a single clip on TikTok racked up more than 70 million views.
She co-wrote it with Michael Pollack and Omer Fedi, who produced it alongside Blake Slatkin.
Spiro has joked she recorded about 900 different versions before landing on the final one, including takes that sounded like Silk Sonic and one that sounded like Lauryn Hill.
This week she launched The Visitor Tour, her first-ever North American headlining run, with a sold-out debut at the Troubadour in Hollywood that drew raves from Variety.
The entire tour sold out within seconds. Additional dates were added due to demand.
Smith and Spiro Have A History Of Amazing Duets
Wednesday’s duet was not the first time Smith and Spiro shared a stage.
Late last year, Spiro opened for Smith during their To Be Free: New York City residency, and the two duetted on Smith’s classic ballad “Lay Me Down.”
Smith later said Spiro “blew the room away,” which is exactly why she was brought out again in San Francisco.
The Castro Theatre itself added another layer to the moment. The venue is a landmark in San Francisco’s LGBTQ+ cultural district and had been closed for two years of renovations.
Smith’s residency is part of its long-awaited reopening, making it an especially fitting stage for what turned out to be a genuinely historic night.
Spiro’s new single “The Visitor” drops March 13. Her tour wraps March 18 in New York City. Smith’s San Francisco residency runs through March 14.
