Robert Devereux, 3rd Earl of Essex, KB, PC was an English Parliamentarian and soldier during the first half of the 17th century. With the start of the Civil War in 1642, he became the first Captain-General and Chief Commander of the Parliamentarian army, also known as the Roundheads. However, he was unable and unwilling to score a decisive blow against the Royalist army of King Charles I. He was eventually overshadowed by the ascendancy of Oliver Cromwell and Thomas Fairfax, and resigned his commission in 1646.

Robert Devereux, 2nd Earl of Essex, KG, PC was an English nobleman and a favourite of Queen Elizabeth I. Politically ambitious, and a committed general, he was placed under house arrest following a poor campaign in Ireland during the Nine Years' War in 1599. In 1601, he led an abortive coup d'état against the government of Elizabeth I and was executed for treason.