The couple confirmed they got married in Las Vegas in a low-key ceremony officiated by an Elvis Presley impersonator. The reception was equally chill as Harbour and Allen ate In-N-Out burgers with her two kids.
The "Stranger Things" actor, 45, wrote on Wednesday on social media: "In a wedding officiated by the king himself, the people’s princess wed her devoted, low born, but kind credit card holder in a beautiful ceremony lit by the ashen skies courtesy of a burning state miles away in the midst of a global pandemic."
Meanwhile, the British singer, 35, posted a series of wedding pics with a simple red heart emoji caption.
Allen donned a white Dior double-breasted off-the-shoulder mini dress with a matching belt and white veil.
Allen and Harbour snagged their marriage approval on Sept. 6, Fox News previously confirmed.
The "Smile" singer was photographed wearing an engagement ring in November, but they both have been coy about their relationship status despite being spotted at sporting events and industry shindigs in the U.S. and abroad.
They were first linked to each other in January 2019.
Allen was previously married to Sam Cooper in 2011 and the pair welcomed two daughters, Marnie Rose, 7, and Ethel Mary, 8. They endured a two-year divorce before finalizing matters in June 2018.
Meanwhile, Harbour previously dated "Fantastic Beasts" star Alison Sudol.
Fox News' Julius Young contributed to this report.