"Day After Day" is a song by the British rock band Badfinger from their 1971 album Straight Up. It was written by Pete Ham and produced by George Harrison, who also plays slide guitar on the recording. The song was issued as a single and became one of Badfinger's biggest hits, charting at number 4 in the United States and number 10 in the UK, ultimately earning gold accreditation from the Recording Industry Association of America.

"Day After Day" was written and sung by Pete Ham and produced by George Harrison, who plays some of the slide guitar parts of the song along with Ham. The record also features Leon Russell on piano. As the song was unfinished at the time Harrison left the Badfinger album to produce the Concert for Bangladesh, the final mix was done by Todd Rundgren, who took over Straight Up after Harrison's departure.

Released as a single in the US in November 1971 (January 1972 elsewhere), it would become the group's highest charting single there, peaking at number 4 on the Billboard Pop Singles chart. It also peaked at number 10 on the UK Singles Chart in January 1972. It remains one of the band's best-known songs, most notably for the slide guitar solos. It went Gold in March 1972, becoming the band's first and only gold single. "Day After Day" reached number 10 on Billboard's Easy Listening survey.