Ut queant laxis or Hymnus in Ioannem is a hymn to Saint John the Baptist written by Paolo Diacono (ca 720 - 799) of Italy. It is notable in that the first syllable of each line gave its name to a successive note of the major scale in solfege, as each line begins with the successively higher note. The lyrics are:
- Ut queant laxis
- Resonāre fibris
- Mīra gestorum
- Famuli tuorum,
- Solve polluti
- Labii reatum,
- Sancte Ioannes.
Ut is now mostly replaced by do due to the latter's open sound. Si has been replaced by ti in English.
The use of Ut queant laxis to name the notes is usually attributed to Guido of Arezzo.