The Roundheads was the nickname given to supporters of the Parliamentarian cause in the English Civil War. The Royalists, on the other side, were the nicknamed Cavaliers.

The Roundheads were so nicknamed because of the relatively short plain page boy style haircuts favoured by Puritans, rather than the long ringlets of the fashionable courtly Cavaliers.

The name started as a term of abuse: in the New Model Army, it was a punishable offence to call a fellow soldier a Roundhead.