The Scottish DJ and producer, real name Adam Richard Wiles, dropped the news on Twitter, adding that he was "very excited" about the track. The tweet also included a first look at the artwork, which depicts a lone tree rising up against a faded pink background.
Smith added his own commentary to the announcement, writing on Twitter: "Surprise!!!! I'm so excited for you all to hear this song."
This won't be the first EDM collaboration of Smith's career, having previously worked with duo Disciples on "Latch".
Harris, meanwhile, has already occupied the top of the charts this year thanks to "One Kiss" featuring Dua Lipa, while also announcing a return to Ibiza for a residency at Pacha.
You can check out the announcement below.
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