Alphonsus may refer to:
As a given nameEdit
- Any of a number of rulers named Alfonso
- Alphonsus J. Donlon (1867–1923), American Jesuit
- Alphonsus Liguori (1696–1787), Roman Catholic Saint
- Alphonsus Liguori Penney (born 1924), Canadian Roman Catholic priest
- Alphonsus Rodriguez (1532–1617), Spanish Jesuit
- Alphonsus a Sancta Maria (1396–1456), Spanish historian
- Alphonsus de Guimaraens (1870—1921), Brazilian poet
- Alphonsus Cassell (1949–2010), Montserratian calypso and soca musician
as a surname:
- Petrus Alphonsi (or Petrus Alfonsus) (1062–1110), Spanish Jewish writer
other:
- Alphonsus (crater) lunar crater