Alphonso or Alfonso (24 November 1273 – 19 August 1284), also called Alphonsus and Alphonse and styled Earl of Chester, was an heir apparent to the English throne who never became king.
Alphonso's eldest brother, John, had died in 1271; the death of another older brother, Henry, in 1274, made Alphonso the couple's only son up until the last months of his life. As his parents were often required to travel, Alphonso had a household of his own. Queen Eleanor was nevertheless invested in the upbringing of her son, who even had a Spanish cook.
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.