Robert Sempill, 3rd Lord Sempill (c. 1505–1576) was a Scottish lord of Parliament. Robert, also Semphill or Semple, 3rd Lord Sempill (d. circa 1575), commonly called the 'Great Lord Sempill', was the elder son of William Sempill, 2nd Lord Sempill, by his first wife, Lady Margaret Montgomery, eldest daughter of Hugh Montgomerie, 1st Earl of Eglinton. His parents' marriage was commemorated in carved stone heraldry at Castle Semple Collegiate Church. Through her paternal grandmother, Lady Margaret Montgomery was a fifth generation descendant from Robert II of Scotland. So descendants of Robert, 3rd Lord Sempill, are descended from many Scottish monarchs up to Robert II, and also from Anglo-Saxon kings (through the marriage of Malcolm III of Scotland to Saint Margaret of Scotland).