Henry I Sinclair, Earl of Orkney, Baron of Roslin (c.1345 – c.1400) is a Scottish and a Norwegian nobleman.
Sinclair holds the title Earl of Orkney under the King of Norway.
He is sometimes identified by another spelling of his surname, St. Clair.
He is the grandfather of William Sinclair, 1st Earl of Caithness, the builder of Rosslyn Chapel.
He is best known today because of a modern legend that he took part in explorations of Greenland and North America almost one hundred years before Christopher Columbus.
William Thomson, in his book The New History of Orkney, wrote: "It has been Earl Henry's singular fate to enjoy an ever-expanding posthumous reputation which has very little to do with anything he achieved in his lifetime."
