Philip Barton Key (April 12, 1757 – July 28, 1815) was a Representative from the third district of Maryland, and later a United States federal judge. Unusually for a politician in the early United States, Key had been a Loyalist in the American Revolution.Born in Charlestown. Cecil County, Maryland, Key pursued an academic course. During the War of Independence he served in the Maryland Loyalists Battalion as a captain.