Sir Frederick Hamilton (c. 1590 – 1647) was a Scottish soldier who fought for Sweden in the Thirty Years' War in Germany and for the Covenanters in Ireland, Scotland, and northern England.

His father's family descended from Walter FitzGilbert, the founder of the House of Hamilton,[1] who had received the barony of Cadzow from Robert the Bruce.

After spending a few years back in Leitrim, he unsuccessfully attempted to re-enter Swedish service in September 1637.

[15] Sir Frederick was involved in a lengthy legal dispute over the ownership of parcels of land in the County of Leitrim with Tirlagh Reynolds of Kiltubbrid.

On 5 December 1640, the committee for Irish affairs of the Long Parliament heard four petitions from Sir Frederick in this respect.

[18][19] Local legend tells that on the way over the mountains back to Manorhamilton Castle, some of his men got lost in heavy fog.

A guide on a white horse offered to lead them safely over the mountain, but intentionally led the men over a cliff and to their doom.

In Ireland he still retained the command of his foot regiment in western Ulster where his sons Frederick and James probably stood in for him.

In 1647, Sir Frederick, aged 57, left the then disbanding army of the Solemn League and Covenant and retired to Edinburgh, where he died later that year in relative poverty.