Katharine Brettargh (1579–1601) was an English Puritan woman from a well-known evangelical Cheshire family, whose early death was made the subject of "godly" biographical commentary.

'It is not unknowne to Lancashire what horses and cattell of her husband's were killed upon his grounds in the night most barbarously at two seuerall times by seminary priests (no question) and recusants that lurked thereabouts.'

It is perhaps characteristic of the times that her biographer insists upon the circumstance that 'she never used to swear an oath great or small.'

After a little more than two years of married life she was attacked by 'a hot burning ague,' of which she died on Whit Sunday, 31 May 1601.

There is a portrait of her in Samuel Clarke's second part of the 'Marrow of Ecclesiastical History,' book ii., London, 1675, p. 52, in an elaborate ruff, the hair closely confined by a sort of skull-cap, over which towers a sugarloaf hat.