Sir William Brereton, 1st Baronet (13 September 1604 – 7 April 1661) was an English writer and politician who sat in the House of Commons at various times between 1628 and 1659. He was a commander in the Parliamentary army in the English Civil War.
Brereton was the son of William Brereton and was baptised at Collegiate Church, Manchester, in 1604. He matriculated at Brasenose College, Oxford on 2 November 1621, aged 18 and was a student of Gray's Inn in 1623. He was then of Handforth Hall, Cheshire. He worked hard to increase the value of his estates. For example, he was interested in field sports and built a duck decoy at Dodleston which became something of a commercial operation. He was created a baronet on 10 March 1627.
In 1628 Brereton was elected Member of Parliament (MP) for Cheshire and sat until 1629 when King Charles I decided to rule without parliament for eleven years. In the summer of 1634 Brereton visited Holland and the Seventeen Provinces and wrote a detailed account of his travels. He took a keen interest in military matters and studied siege warfare there at first hand. In the following year from 11 June to 4 August he journeyed through north eastern England to lowland Scotland and thence to Ireland, returning to land in England at Minehead from where he made his way back to Chester. In other years he journeyed in France and other parts of England although his records of the journeys have been lost.
In April 1640, Brereton was re-elected MP for Cheshire in the Short Parliament. He was re-elected for the Long Parliament in November 1640. He took a stand against King Charles by organising a petition, said to contain over 1000 signatures, directed against episcopacy - rule of the Church by bishops.