Frederick Cornwallis, 1st Baron Cornwallis (14 March 1610/1 – January 1662) was an English peer, MP and Privy Counsellor. He was the eldest surviving son of Sir William Cornwallis of Brome, Suffolk, and his second wife, Jane. After his father's death, his mother married Sir Nathaniel Bacon.
He married twice. His first wife, Elizabeth Ashburnham, was the daughter of Sir John Ashburnham (of Ashburnham and Penhurst, Sussex) and Elizabeth Richardson, 1st Lady Cramond. They had three sons (of which only one, Charles, outlived him), and a daughter. After her death c. February 1643, he married Elizabeth Crofts, daughter of Sir Henry Crofts (of Little Saxham), with whom he had a daughter.
He was the father of Charles Cornwallis, 2nd Baron Cornwallis; the grandfather of Charles Cornwallis, 3rd Baron Cornwallis; the great-grandfather of Charles Cornwallis, 4th Baron Cornwallis; the 2nd great-grandfather of Charles, Stephen, Edward, and Frederick Cornwallis; the 3rd great-grandfather of Charles, William, and James Cornwallis; the 4th great-grandfather of Charles Cornwallis, 2nd Marquess Cornwallis; the 5th great-grandfather of James Mann; the 6th great-grandfather of Fiennes Cornwallis; the 7th great-grandfather of Fiennes Cornwallis, 1st Baron Cornwallis; the 8th great-grandfather of Wykeham Cornwallis, 2nd Baron Cornwallis; and the 9th great-grandfather of Fiennes Cornwallis, 3rd Baron Cornwallis.