A defiant grassroots fan-favorite, a viral TikTok smash, and several cross-genre collaborations all made it into the top 10 highest-selling country songs for 2021.

Billboard issued its year-end tallies earlier this month, including a list of country songs that raked in the most digital sales this year. For a couple of songs in this collection, it wasn't their first time making the list. Gabby Barrett"s "I Hope," which had the highest digital sales of any country song in 2020, remains firmly in the Top 10 this year, sliding in at No. 8.

Meanwhile, Chris Stapleton's "Tennessee Whiskey" holds dominant in 2021, six years after the song's initial release. It ranked high in digital song sales last year, too. Not only do Stapleton and Barrett both have songs with apparent staying power, but they're also continuing to rack up new hits: Each of them had another song in the Top 10. For Barrett, that was her country radio chart-topper, "The Good Ones," and Stapleton saw success with "Starting Over," the title track and lead single of his latest album.

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While "Tennessee Whiskey"'s been out for six years, it appeared alongside another song that hasn't even been out for six months: Carrie Underwood and Jason Aldean's hit collaboration "If I Didn't Love You" clocks in at No. 9, after racing up the country radio charts to hit No. 1 earlier this year.

But the biggest seller of the year was a chart-topping, odds-defying, genre barrier-breaking viral smash that got its start on TikTok and even led to a promo partnership with Applebee's. Can you guess the song?

Here Are the Top-Selling Digital Country Songs of 2021

Billboard has released its year-end list of top-selling digital country songs, and hits by Walker Hayes, Gabby Barrett, Jason Aldean and more are among them.