Clan Gregor or Clan MacGregor (Scottish Gaelic: Clann Ghriogair [ˈkʰl̪ˠãũn̪ˠ ˈɣɾʲikɪɾʲ]) is a Highland Scottish clan dating back to the early 800s. The clan's most famous member is the legendary Rob Roy MacGregor of the late 17th and early 18th centuries. The Clan is also known to have been among the first families of Scotland to begin playing the bagpipes in the early 17th century.

The Clan Gregor held lands in Glen Orchy, Glenlochy and Glenstrae. According to Iain Moncreiffe the MacGregors were descended from an ancient Celtic royal family, through the Abbots of Glendochart. This is alluded to in the clan's motto: "Royal is my race". There is also a tradition that Gregor was the son of Kenneth MacAlpin, which is supported by the Scottish historian, William Forbes Skene, but there is little evidence to support this tradition. It is possible that he might have been Griogair, son of Dungal, who was allegedly co-ruler of Alba.

Most modern historians have agreed that the first chief of Clan Gregor was Gregor of the golden bridles. His son was Iain Camm One eye, who succeeded as the second chief sometime before 1390.

The barony of Loch Awe which included much of the MacGregor lands was granted to the chief of Clan Campbell by Robert the Bruce. The Campbells had already built Kilchurn Castle which controlled the gateway to the western Highlands and they harried the MacGregors who were forced to retire deeper into their lands until they were restricted to Glenstrae.

Iain of Glenstrae died in 1519 with no direct heirs. He was the second of his house to be called the Black. The succession of Eian was supported by the Campbells, and he married a daughter of Sir Colin Campbell of Glenorchy. In 1547 Eian's son, Alistair, fought against the English at the Battle of Pinkie Cleugh but died shortly after.

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