"Old Town Road" featuring Billy Ray Cyrus broke the US record in July for the longest time a song had spent in the number one spot, over-taking the joint record of 16 weeks held by Luis Fonsi, Daddy Yankee and Justin Bieber with 2017's "Despacito", and Mariah Carey and Boyz II Men with "One Sweet Day".
The track made headlines in March after it was removed from the Billboard Hot Country Songs chart, despite including many traditional qualities of a country song.
However, this only increased the song's popularity, and until this week the Billy Ray Cyrus version had been at the top of the charts since 13 April.
Both Nas and Cyrus congratulated 17-year-old Eilish on her achievement, with Nas writing: "Congratulations to Billie Eilish!! U deserve this!! [sic]." He also joked about being dropped from his record label after slipping from the top spot.
congratulations to billie eilish!! u deserve this!!— nope (@LilNasX)August 19, 2019
Cyrus tweeted: "Congratulations @billieeilish. Well deserved. Your persistence paid off. Thanks everybody. It was a hell of a ride."
— Billy Ray Cyrus (@billyraycyrus)August 19, 2019
Eilish will perform at Reading and Leeds festivals this weekend (24-25 August).