Colonel Alexander Ranaldson MacDonell of Glengarry (15 September 1773 – 17 January 1828), sometimes called by the Gaelic version of his name, Alastair or Alasdair, was clan chief of Clan MacDonell of Glengarry. As was customary for a laird (landed proprietor in Scotland), MacDonell was often called Glengarry after his principal estate.