Illegitimate son of Charles II., born at Rotterdam; was admitted to Court after the Restoration, and received his title in 1663; his manners and his Protestantism brought him popular favour in spite of his morals, and by-and-by plots were formed to secure the succession for him; forced to fly to Holland in 1683, he waited till his father's death, then planned a rebellion with Argyll; Argyll failed in Scotland; Monmouth, landing in Dorsetshire 1685, was soon overthrown at Sedgemoor, taken prisoner, and executed (1649-1685).