Henry I Sinclair, Earl of Orkney, Baron of Roslin (13451400) was a Scottish and a Norwegian nobleman. Sinclair held the title Earl of Orkney under the King of Norway (see Earl of Orkney: Scottish Earls under the Norwegian Crown). He is sometimes identified by another spelling of his surname, St. Clair. He was 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 100 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."