"Young Girl" is a RIAA million-selling Gold-certified single that was written, composed, and produced by Jerry Fuller and performed by Gary Puckett & The Union Gap with instrumental backing by members of "The Wrecking Crew." It was released in 1968.

The song hit No. 2 on the Billboard Hot 100 for three weeks, stuck behind "(Sittin' On) The Dock of the Bay" by Otis Redding for the first week and "Honey" by Bobby Goldsboro for the remaining two. It also hit No. 1 on the UK Singles Chart and the US Cash Box listing. It reached No. 34 on the US Easy Listening. It reached No. 2 in South Africa.

The song is sung from the point of view of a man who has become distressed upon finding out that the girl he is with, contrary to the first impression she had made upon him, is actually younger than the legal age of consent. He is asking her to leave before things go any further: "Get out of here / before I have the time / to change my mind / 'cause I'm afraid we'll go too far."

In the UK, "Young Girl" was re-released in 1974 as a double A-sided single with "Woman, Woman". This re-release was part of a CBS Records series entitled "Hall of Fame Hits". As a result of the re-release, "Young Girl" enjoyed a second UK chart run, peaking at No. 6.