Henry Sinclair, 2nd Earl of Orkney (c. 1375 – 1420) was a Norwegian nobleman and Pantler of Scotland.
He was son of Henry Sinclair, 1st Earl of Orkney by his wife Jean, daughter of John Halyburton of Dirleton. Sinclair was one of those captured following the Battle of Homildon Hill in 1402, but released on ransom. He had succeeded his father by 1404, and was one of those who accompanied James Duke of Rothesay on his journey to France aboard the Maryenknyght, which was captured by English pirates off Flamborough Head in 1406. He followed the prince into captivity, but was soon released. Subsequently he was often in England on business connected with the king's imprisonment. He also spent some time in the service of the Duke of Burgundy. There is no record that he was ever officially installed as Earl, and no certain record that he ever visited his earldom.
Henry Sinclair died of influenza c. 1420.
In about 1407 he married Egidia Douglas, daughter of Sir William Douglas of Nithsdale and maternal granddaughter of King Robert II of Scotland.