Colonel Edward Sexby or Saxby (1616 – 13 January 1658) was an English Puritan soldier and Leveller in the army of Oliver Cromwell. Later he turned against Cromwell and plotted his assassination.
Sexby was born in Suffolk in 1616 but little else is known about his life before the English Civil War. Reportedly he was a son of a gentleman, had been an apprentice as a grocer in London and may have had family connections to Cromwell. In 1643 he was a trooper in Cromwell's Roundhead cavalry regiment (nicknamed the Ironsides).
In 1647, being still a private in the same regiment, now commanded by Sir Thomas Fairfax, he took a leading part in the movement against disbanding the army, and was one of the three soldiers charged with the letter from the army to their generals which Skippon brought before the House of Commons on 30 April 1647. He became one of the leaders of the "Agitators", and acted as their chief spokesman in the Putney Debates of the Army Council in October 1647. His speeches were very vigorous and effective, opposing all compromise with King Charles I and demanding the immediate establishment of manhood suffrage. He may have been involved in the capture of the king at Holdenby House in 1647.
Sexby appears to have left the army about the close of 1647, but happening to be present at the Battle of Preston, with a letter from the Levellers leader John Lilburne to Cromwell, he was entrusted with a despatch from Cromwell to the speaker of the House of Commons announcing his victory. The House of Commons voted him £100 as a reward. In February 1649 Parliament entrusted him with the duty of arresting the Scottish commissioners, for which he was ordered £20. He was also appointed governor of Portland, is henceforth described as Captain Sexby, and was more than once charged with commissions requiring courage and dexterity.