Alphonso, Earl of Chester

Alphonso as portrayed in a genealogical roll of the kings of England, from southern England, first quarter of the 14th century, before 1308

Alphonso, Earl of Chester (24 November 1273 – 19 August 1284) was the ninth child of Edward I of England and Eleanor of Castile. During his life, he was first in line to his father's throne of England and to his mother's county of Ponthieu in France.

Alphonso was born at Bayonne, in Gascony, and named after his maternal uncle, Alfonso X of Castile, who was his godfather. At the age of ten, he was engaged to Margaret, daughter of Floris V, Count of Holland. An opulent psalter was being prepared for the marriage when he died, a few months before the wedding was to take place. The Alphonso Psalter was completed a decade later when his sister Elizabeth married Margaret's brother, John I, Count of Holland, making the pairing of arms again appropriate.

Alphonso's coat-of-arms and Margaret's, from his eponymous psalter

Alphonso's death at Windsor occurred shortly after the birth of his younger brother Edward, who became the oldest surviving male heir of Edward I. Alphonso was interred in The Confessor's Chapel at Westminster Abbey, although the exact location is unknown. His heart, however, was buried at the priory of Blackfriars, London (now destroyed).

As heirs-apparent to the throne, both Alphonso and Edward bore the arms of the kingdom, differenced by a label azure of three points.