"What a Difference You've Made in My Life" is an inspirational song written by Archie Jordan and first made famous by two artists during 1977: then-teenage Christian music singer Amy Grant and country music singer Ronnie Milsap.
Amy Grant's version was included on her self-titled debut album, which was sold largely in Christian bookstores and outlets. The song was released as a single to Christian-oriented radio stations, charted at No. 5 on the US Christian charts, and helped Grant become well known in what was then a small sub-genre of religious-themed music.
However, Milsap's version became better-known. It was released in November 1977 as the second single from the album It Was Almost Like a Song. The song soon scored the Billboard Hot Country Songs chart and was his ninth No. 1 song on that chart. Milsap re-recorded the song for his 2009 country gospel album, Then Sings My Soul.
In 1978, B. J. Thomas covered the song on his Happy Man album, which became a Top 10 Christian hit.