right|thumb|200px|The 1st Marquess of Lothian.
Robert Kerr, 1st Marquess of Lothian (8 March 1636 – 15 February 1703), known as the 4th Earl of Lothian from 1675 to 1701, was a Scottish nobleman. He was styled Lord Kerr until 1661 and Lord Newbattle from 1661 to 1675.
The eldest son of William Kerr, 3rd Earl of Lothian and Anne Kerr, he was born at Newbattle Abbey, Midlothian. He left Scotland and was educated at Leyden, Saumur, and Angers from 1651 to 1657. He unsuccessfully claimed the earldom of Roxburghe in 1658. In 1661, his father lost an additional dispute with the new Earl of Roxburghe over the use of the courtesy title of Lord Kerr; it was reserved for Roxburghe's heir, and Kerr was thereafter styled Lord Newbattle.
Lord Newbattle was a volunteer in the Dutch War of 1673. He succeeded his father in the earldom in 1675. Sworn a Privy Counsellor in January 1686, he was removed by James II in September. Lothian supported the Glorious Revolution and sat in the Convention of Estates of Scotland. He was appointed Lord Justice General of Scotland in 1689, holding the office until his death, and was re-appointed a privy counsellor by William III in 1690. In the same year, he succeeded his uncle Charles as Earl of Ancram.