Robert Marsham, 1st Baron Romney (17 September 1685 – 28 November 1724), known as Sir Robert Marsham, Bt, between 1703 and 1716, was an English politician who sat in the House of Commons from 1708 to 1716 when he was raised to the peerage as Baron Romney.
Marsham was the son of Sir Robert Marsham, 4th Baronet of Bushey Hall, Hertfordshire, and his wife Margaret Bosvile, daughter of Thomas Bosvile of Little Motte, Eynsford, Kent. His father was a former MP for Maidstone. Margaret, granddaughter of Sir Francis Wyatt, was heir to the Wyatt family seat and passed Boxley Manor to her son. Marsham was educated at St John's College, Oxford (matriculated 1701) and succeeded his father as the 4th Baronet in 1703.
He was elected Member of Parliament (MP) for Maidstone in 1708 and held the seat until 1716. He was raised to the peerage as Baron Romney, of Romney in the County of Kent, on 22 June 1716 and was constituted governor of Dover Castle in 1717.
He was elected a Fellow of the Royal Society in 1723.
He died in November 1724, aged 39, and was buried in Crayford, Kent. Lord Romney had married Elizabeth Shovell, daughter of Admiral Sir Cloudesley Shovell, in 1708. He was succeeded by their son, Robert. Lady Romney married as her second husband John Carmichael, 3rd Earl of Hyndford, and died in November 1750, aged 58