English military commander and statesman who from 1443 to 1450 dominated the government of the weak king Henry VI (ruled 1422–61 and 1470–71). He was popularly, although probably unjustly, held responsible for England's defeats in the late stages of the Hundred Years' War (1337–1453) against France.

When his father, Michael de la Pole, 2nd Earl of Suffolk, was killed fighting the French at the Battle of Agincourt in 1415, William succeeded to the earldom of Suffolk. He served in all the French campaigns of King Henry V from 1417 to 1422 and became one of the most trusted generals of Henry VI. In 1428 Suffolk was made commander in chief of the English army in France, but on June 12, 1429, he was defeated and taken prisoner by Joan of Arc (Joan of Arc, Saint) at Jargeau. Upon being ransomed, he held his former command until recalled to England late in 1431.

During the next decade Suffolk served as a royal councillor and emissary. He acquired considerable influence in the government by joining the faction of Henry Cardinal Beaufort, which dominated the king, and, after Beaufort's retirement in 1443, Suffolk became Henry VI's chief adviser. In an effort to end the war, he secured a two-year truce in 1444, but he enraged his countrymen by ceding the provinces of Maine and Anjou to France. Nevertheless, he was created Duke of Suffolk in 1448, and this marked the height of his power.

Suffolk's downfall came after the English treacherously captured Fougères—probably with his approval—in March 1449, thereby reopening hostilities. Soon the French recaptured almost all of Normandy. Parliament laid the blame for the disaster on Suffolk, and with great reluctance the king banished the duke from the realm for five years. Suffolk left England on May 1, 1450, but he was intercepted in the English Channel by some of his enemies and beheaded. He died without surviving issue, and his titles became extinct.