The Fifth Monarchy aka The Fifth Monarchists aka The Fifth Monarchy Men aka the "Fifth Kingdom" was a Protestant, or more correctly a radical Puritan led Protestant movement in England from 1649 - 1661, based upon the prophesies of Daniel 2: 44 and the wide-spread idea that the Second Coming of Christ was immanent (pun), as was the rising of the Devil as the Beast 666 of Revelations, in the year 1666.
England was in chaos, having executed King Charles I in January 1649 and the Civil War raged from 1642 – 1651, devastating the countryside. The plague returned in 1664, and the Great Fire which reduced London to ash in September of 1666. Rebuilding all that was lost seemed a daunting task, and many looked at the destruction and saw God's hand rather than Man and Nature's fault.
One religious movement, the Fifth Monarchy, preached that God HIMself would next rule (1st England, then) the world, and they would become an Army of Saints marching to Victory as HIS Hosts. Leaders of Oliver Cromwell's New Model Army took that political / Command structure and applied it to a religious mob. It's leaders were Christopher Feake (1612-1683?) of Christ Church (Newgate) @ 1649; John Rogers (1627-1665?) from Dublin @ 1652; John Canne (1590?-1667?) of the Robert Overton Regiment at Hull; John Simpson (d. 1662); Vavasor Powell (1617-1670); Robert Blackborne, Secretary of the Admiralty; Major-General Thomas Harrison; John Carew; John Rogers; Major-General John Lambert; John James; Thomas Venner, leader of Venner's Rising, 1661; and of course, "God's Instrument" Oliver Cromwell, the Lord Protector and Killer of Kings.
Opposed by the Royalists like Elias Ashmole ans John Wilkins, The Fifth Monarchists influenced the Barebone's Parliament (July-December 1653) and remained defiant after the new Commonwealth paid off the New Model Army and suppressed the Levelers, an early version of the Occupy movement of modern times. But as the new British government was created, there were practical matters to deal with, and the resulting lack of a Christian Utopia with charity replacing taxes was not realized, and the theocracy desired by The Fifth Monarchists was never implemented.
This led to a rift between The Fifth Monarchists and Cromwell's government, made much worse with the return of the King's son, Charles II. To "save" the revolution and country, Thomas Venner planned an abortive coup, Venner's Rising, in 1661. It continued as a religious, if not political movement, into the 1700s.
In many ways, their beliefs are a resurgence of the Judges movement in Ancient Judea, where before King Saul (and then David and King Solomon) the Tribes were ruled by Judges, because God was the only King. Fifth Monarchists battled to make Jesus King on England in Spirit, which they hoped would coax the Apocalypse and Judgement Day.
Gerrard Winstanley's True Levellers in 1649, later known as The Diggers, were even more socialistic.