Dion Francis DiMucci (born July 18, 1939), better known mononymously as Dion, is an American singer, songwriter whose work has incorporated elements of doo-wop, rock and R&B styles--and, most recently, straight blues. He was one of the most popular American rock and roll performers of the pre-British Invasion era. He had 39 Top 40 hits in the late 1950s and early 1960s as a solo performer, with the Belmonts or with the Del Satins. He is best remembered for the singles "Runaround Sue", "The Wanderer", "Ruby Baby" and "Lovers Who Wander", among his other hits.

By the end of 1960, Dion had released his first solo album on Laurie, Alone with Dion, and the single "Lonely Teenager," which rose to No. 12 in the US charts. The name on his solo releases was simply "Dion." Follow-ups "Havin' Fun" and "Kissin' Game" had less success, and the signs were that Dion would drift onto the cabaret circuit. However, he then recorded, with a new vocal group, the Del-Satins, an up-tempo number co-written with Ernie Maresca. The record, "Runaround Sue," stormed up the U.S. charts, reaching No. 1 in October 1961, and No. 11 in the UK, where he also toured. "Runaround Sue" sold over a million copies, achieving gold disc status.  For the next single, Laurie promoted the A-side, "The Majestic," but it was the B-side, Maresca's "The Wanderer," which received more radio play and climbed swiftly up the charts to reach No. 2 in the U.S. in February 1962 and No. 10 in the UK (the 1976 re-release made the UK Top 20). "The Wanderer" has been used in the post-apocalyptic role-playing game Fallout 4, both in-game and in a trailer of the same name released in 2015.  By the end of 1961, Dion had become a major star, touring worldwide and making an appearance in the Columbia Pictures musical film Twist Around the Clock. He followed with a string of singles - "Lovers Who Wander" (No. 3), "Little Diane" (No. 8), "Love Came to Me" (No. 10) - in 1962, several of which he wrote or co-wrote. He also had successful albums with Runaround Sue and Lovers Who Wander.  At the end of 1962, Dion moved from Laurie to Columbia Records; he was the first rock and roll artist signed to the label, which was an anomaly considering that its then-A&R director, Mitch Miller, passionately loathed that particular genre of music. The first Columbia single, Leiber and Stoller's "Ruby Baby" (originally a hit for the Drifters) reached No. 2, while "Donna the Prima Donna" and "Drip Drop" (another remake of a Drifters hit) both reached No. 6 in late 1963. (Dion also recorded an Italian version of "Donna the Prima Donna" using the identical backup vocals.) His other Columbia releases were less successful, and problems with his addiction and changing public tastes, especially The British Invasion, saw a period of commercial decline.

Why did he leave the Belmonts?