Which song became Diana Ross's sixth and final single to reach No.1 on the Billboard Hot 10?

The soulful 1981 song composition "Endless Love" became the biggest-selling single of Ross' career. It is her sixth single as a solo music artist to reach No. 1 on the Billboard Hot 10. It is her 18th and final career No. 1 single (including her work with the Supremes) to be on this chart. It is also Richie's biggest charting single, and the first of several hits for him during the 1980s. The song was further nominated for an Academy Award for Best Original Song for Richie, and was the second song with which Ross was involved that was nominated for an Oscar.

“Endless Love” is a song written by Lionel Richie and originally recorded as a duet between Richie and fellow R&B (soul) singer Diana Ross. It was recorded for the eponymous 1981 movie "Endless Love" starring Brooke Shields (which in turn adapted a novel). In this ballad, the singers declare their “endless love” for one another.

The song went to No. 1 in Australia, Canada and the US that summer. In 2011, Billboard named it the biggest duet of all-time.

It was later covered by soul singer Luther Vandross with R&B singer Mariah Carey, and also by country music singer Shania Twain. Richie’s friend (and sometimes co-worker) Kenny Rogers has also recorded the song.