När en vacker tanke blir en sång ("When a Beautiful Thought Becomes a Song") is the fourth Swedish solo album by Swedish pop singer and ABBA member Agnetha Fältskog, which was released in the end of 1971.

The recording of the album took place on various occasions during 1971, beginning in May, continuing through July and October and ending on 4 November.

As with her previous albums, the recording was assisted by Michael B. Tretow and features Sven-Olof Walldoff and his choir and orchestra.

The album's only cover version, "Dröm är dröm, och saga saga", which was a radio-only single in the end of 1971, was the most successful and eventually reached the top 3 in the end of December, while Agnetha's own composition "Många gånger än" reached the top 5 some months earlier.

The beginning of 1972 marked the rare occasion of a none-single track showing up on Svensktoppen, namely "Sången föder dig tillbaka", which cracked the top 10 for one week in February.