"Hello Mary Lou" is a song written by U.S. singer Gene Pitney and Cayet Mangiaracina, first recorded by Johnny Duncan in 1960, and later by Ricky Nelson in 1961.Nelson's version, issued as the B-side of his No. 1 hit "Travelin' Man", (Imperial 5741), reached No. 9 on the Billboard music charts on May 28, 1961. In the United Kingdom, where it was released as an A-side (with Dorsey Burnette's "It's Late" as the B-side), it reached No. 2.