Monstrous regiment, or monstrous regiment of women are phrases which have become notorious; they are borrowed from the title of a work by the Reverend John Knox, published in 1558, The First Blast of the Trumpet Against the Monstrous Regiment of Women. The word regiment is used here in its etymological sense, meaning "government"; the contemporary evocation of a fearsome military sisterhood makes the title even more colorful now than originally.
The book was written anonymously from Geneva, against the female sovereigns of his day, particularly Mary, Queen of Scots and Mary Tudor. Knox, a staunch Protestant, opposed the Roman Catholic queens on religious grounds, and on their account he poured upon their whole gender some of the most memorable misogynistic invective ever recorded in political history:
His diatribe against female rulers backfired on him when Elizabeth Tudor succeeded her half-sister Mary on the throne of England: Elizabeth was a supporter of the Protestant cause, but took offense at Knox's words about female sovereigns. Her opposition to him personally became an obstacle to Knox's direct involvement with the Protestant cause in England after 1559.