"I Honestly Love You" was a worldwide pop hit single for Olivia Newton-John in 1974. The song was Newton-John's first number-one single in the United States and Canada, thus cementing her as a household name in North America. Released on the Long Live Love album in the United Kingdom, it was eventually released on the album If You Love Me, Let Me Know in the United States. Peter Allen recorded it around the same time on his album "Continental American"

The song topped the charts in America on October 5 and went on to sell over two million copies, being certified Platinum. It also reached number one (three weeks) on the Adult Contemporary charts and number six on the Country charts, and won Grammy Awards for Female Pop Vocal Performance and Record of the Year. The song's success also helped propel its parent album, If You Love Me, Let Me Know, to number one; the title song was released as a single prior to "I Honestly Love You" and was also a top-five multi-format (Pop - No. 5, Adult Contemporary - No. 2, and Country - No. 6) hit. By contrast, the single failed to reach the top-twenty in the UK, although it did re-chart there in 1983 when re-released to promote a Newton-John greatest hits album.

Newton-John re-released the original hit version of the song in 1977, backed with "Don't Cry For Me Argentina" from her then-current album Making a Good Thing Better, and it reached number forty-eight Pop (outperforming the only single from Making A Good Thing Better, the title song, which stalled at number eighty-seven). The song also recharted AC at No. 49. In 1998, she released a new version of "I Honestly Love You" from her album Back With a Heart, which featured Babyface on background vocals and reached number sixty-seven on the Billboard Hot 100, her first U.S. chart single in six years. The 1998 version also charted AC (No. 18) and Country Sales (No. 16). The song was briefly mentioned in the 2001 film The Wedding Planner, which starred Jennifer Lopez and Matthew McConaughey. Lopez's character Mary mentions that any couple who chooses the song for their wedding song is doomed to divorce in under a year.

During the 1990s, this song was used in Australia to advertise tourism for Tasmania.

The song is performed in the musical The Boy from Oz.