List of Best Selling Rhythm & Blues Singles number ones of 1968

In 1968, Billboard published a weekly chart ranking the top-performing singles in the United States in rhythm and blues (R&B) and related African American-oriented music genres; the chart has undergone various name changes over the decades to reflect the evolution of such genres and since 2005 has been published as Hot R&B/Hip-Hop Songs. It was published under the title Top Selling R&B Singles in the issue dated January 6, 1968, Best Selling R&B Singles through the issue dated March 30, and Best Selling Rhythm & Blues Singles thereafter; during the year, 20 different singles topped the chart.

Unusually, the year started and ended with different versions of the same song at number one. In the issue of Billboard dated January 6, Gladys Knight & the Pips were at number one with "I Heard It Through the Grapevine", the song's sixth week in the top spot. In December, Marvin Gaye's version of the song reached number one and held the peak position for the final three weeks of the year. Gaye had actually recorded his version before Knight recorded hers, but Berry Gordy, owner of the Motown record label, refused to allow it to be released. After Knight's version became a success, Gaye's version was included on his album In the Groove and was released as a single by popular demand. It ultimately outperformed Knight's version, becoming Motown's biggest-selling single to date, and has come to be regarded as the definitive version of the song. It was Gaye's third chart-topper of 1968, following "Ain't Nothing Like the Real Thing" and "You're All I Need to Get By", both duets with Tammi Terrell.

In March, Otis Redding reached number one with his song "(Sittin' on) the Dock of the Bay", which spent three weeks in the top spot. Redding had died in a plane crash in December of the previous year just days after recording the track, which in addition to topping the R&B listing became the first posthumous number one on the all-genre Hot 100 chart. "Tighten Up" by Archie Bell & the Drells, "Grazing in the Grass" by Hugh Masekela and Gaye's version of "I Heard It Through the Grapevine" also topped both charts in 1968. Redding, Bell & the Drells and Masekela all topped the R&B chart in 1968 for the first time, as did Tammi Terell, the Intruders, the Dells and Johnnie Taylor. The Dells were inducted into the Rock and Roll Hall of Fame in recognition of their long and successful career, and the Intruders are considered to have been an early influence on the Philadelphia soul sound, which grew in prominence in the 1970s.