"I Knew You When" is a song written and composed by Joe South. It became a popular hit in 1965 when recorded by American pop and country singer Billy Joe Royal. There have also been several other hit cover versions of this song, including Donny Osmond and Linda Ronstadt.

"I Knew You When" was first recorded by Billy Joe Royal for his 1965 studio album, Down in the Boondocks. The song reached No. 14 on the Billboard Hot 100 in 1965. The song went to No. 1 on the Canadian music chart in November 1965.

Donny Osmond released a version in 1971 as the B-side of "Hey Girl" that went to No. 9 on the Hot 100 as a double-sided hit. On the Cashbox chart, where it was listed as its own side, it reached #83.

Linda Ronstadt recorded a cover version for her Gold-plus 1982 album, Get Closer. Her single was produced by Peter Asher and released on Asylum Records. Aided by a popular music video, it reached #30 on the Cash Box Top 100 chart and #37 on the Billboard Hot 100 as the album's second single.

Additionally, it reached No. 29 on the adult contemporary chart, No. 84 on the country chart, and No. 90 in the United Kingdom.

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