The star – whose single Sorry Not Sorry is currently scaling charts worldwide – put her impressive vocals to good use as she stepped up to open the night with the National Anthem.
Although some viewers complained that her rendition was too long, many were quick to heap praise.
“Forgot to mention this: Demi Lovato had the best national anthem since Whitney Houston,” said one.
“Ok but can we talk about how great of a vocalist Demi Lovato is? Amazing,” said another.
Many others joked that the former Disney starlet overshadowed the actual fight.
Ashley Greene posted: “Wow! This @ddlovato concert is amazing!”
Ryan Good even quipped: “@ddlovato won.”
Yet another post read: “Demi lovato SLAYED her performance and thats all there is to say!!!!!”
“Demi Lovato really just slayed the National Anthem in front of 100M people. I love a legend,” said someone else.
The star herself wrote: “Thank you for having me in the ring tonight!! #MayweathervMcgregor.”
She is due to release her new album Tell Me You Love Me on September 29, putting her in direct competition with Miley Cyrus and Shania Twain.
She released the title track from the LP last week.