The term "Roundheads" refers to the supporters of the Parliament during the English Civil War (1642-1651). They were primarily composed of Puritans and other groups who opposed the monarchy, particularly the rule of King Charles I. The name "Roundhead" originated from their short haircuts, which contrasted with the long hairstyles of the royalist supporters, known as Cavaliers. Roundheads played a significant role in the conflict, advocating for greater parliamentary power and religious reforms. Their military leader, Oliver Cromwell, emerged as a key figure, leading the New Model Army to several important victories. Ultimately, the Roundheads' efforts contributed to the temporary overthrow of the monarchy in England.