Montagu was the son of Edward Montagu, 2nd Earl of Manchester and his second wife Lady Anne Rich, daughter of Robert Rich, 2nd Earl of Warwick. He was born in the parish of Saint Margaret"s, Westminster, and baptised there on 25 April 1634.
From 1649 to 1654, he was travelling abroad. He was captain of the militia horse for Huntingdonshire in April 1660. He was a Justice of the Peace for Huntingdonshire and Northamptonshire, from July 1660 to 1681.
Also in July, he was commissioner for oyer and terminer for the Midland circuit.
From August 1660, he was commissioner for assessment and Deputy Lieutenant for Huntingdonshire until 1671. In 1661, Montagu was again elected Member of Parliament for Huntingdonshire in the Cavalier Parliament.
In 1663, he became commissioner for assessment for Huntingdon and Northamptonshire until 1671, and was sent on a mission to the French king. He was created Master of Arts by the university of Oxford, on 8 September 1665.
In February 1666, he succeeded the Earl of Newport as gentleman of the bedchamber to the king.
In 1666 and 1667 Montagu was a captain of the Duke of Monmouth’s Horse in the eastern counties while the Dutch were on the coast. Montagu inherited the title of Earl of Manchester on the death of his father in 1671 and took on the posts of Lord Lieutenant of Huntingdonshire and Custos Rotulorum In 1672 he became master of the swans and also water-bailiff for Whittlesey Mercantile He became high steward of Cambridge University in 1677.
In October 1681 Lord Manchester decided to go abroad because he had become too closely involved with cabalistic men in Northamptonshire.
He died at Montpellier in France at the age of about 48 and was buried at Kimbolton. Honorary Edward. Honorary Henry.
Lady Anne Montagu (c 1667–1720), married James Howard, 3rd Earl of Suffolk. Charles Montagu, 1st Duke of Manchester (c 1656–1722)
Lady Elizabeth Montagu (b c 1682)
Lady Catherine Montagu, married Samuel Edwin
Honorary
Robert Montagu (d 1693)
Honorary
Heneage Montagu (1675–1698)
Lady Eleanor Montagu, died unmarried. His widow afterwards married Charles Montagu, 1st Earl of Halifax.
Cavalier Parliament]
Also in April 1660, Montagu was returned as Member of Parliament for Huntingdonshire in the Convention Parliament and in the following month was one of the members who waited on the king at the Hague.
