Colonel Robert Lilburne (1613–1665) was the older brother of John Lilburne, the well known Leveller. Unlike his brother, who severed his relationship with Oliver Cromwell, Robert Lilburne remained in the army. He is also classed as a regicide for having been a signatory to the death warrant of King Charles I in 1649. He was forty-seventh of the fifty nine Commissioners.
At the outbreak of the First English Civil War Lilburne joined the Roundheads. He served under Edward Montagu (the son of Earl of Manchester) and by 1644 had attained the rank of captain. He then raised a regiment of horse in County Durham which became part of Lord Fairfax's Northern Association army. He joined the New Model Army and was promoted to Colonel of a regiment.
Although like his brother John, his sympathies like those of his regiment lay with the Levellers, he was not present at the Corkbush Field rendezvous, the first of several meetings planned following the Putney Debates. Robert Lilburne's regiment marched, without orders, to the rendezvous in the hope of pressing the Levellers manifesto, the Agreement of the People, on the Army. The mutiny failed. Along with copies of the Agreement, the soldiers displayed in their hats papers showing the Levellers' slogan, "England's Freedom, Soldiers' Rights". When an officer of the commander of the Army, Sir Thomas Fairfax approached them, members of Lilburne's regiment stoned and wounded him. Oliver Cromwell, then the second-in-command of the New Model Army, and some of his officers rode into their ranks and ordered them to take the papers from their hat bands. Cromwell had eight or nine of the more truculent of Lilburne's troopers arrested, tried at an improvised court-martial, and found guilty of mutiny. Three ringleaders were sentenced to death and, having cast lots, Private Richard Arnold was shot on the spot as an example.