He was born at Litton, Derbyshire, in the parish of Tideswell, on 17 January 1628, the son of William Bagshaw of Hucklow. He received his early education at country schools, and met puritan ministers Rowlandson of Bakewell and Bourn of Ashover. He entered Corpus Christi College, Cambridge in 1646. He preached his first sermon in the chapel of Wormhill, in his native parish. From Tideswell he moved to Attercliffe, in Yorkshire. Here he occupied a twofold post, being assistant to the Rev. James Fisher of Sheffield, and chaplain in the family of Colonel John Bright. He received presbyterian ordination in 1651 at Chesterfield, and after some time was presented to the living of Glossop.
After the Restoration and the Act of Uniformity 1662 he gave up his living and retired to Ford Hall near Chinley, in an adjacent parish. He lived as a country gentleman, attended the parish church, but continued to preach and regularly conducted a service on Thursday evenings in his own house. After the Declaration of Indulgence of 1672, he felt free to preach regularly in his former parish and in the neighbourhood. He lectured at Ashford, Malcoff, Middleton, Bradwell, Chelmorton and Hucklow. When the Declaration was recalled by Charles II, he continued to preach secretly. There were several ineffective warrants issued against him. While James II's 'Declaration for Liberty of Conscience' was in force, and again through the beginning of William and Mary's reign, he was an incessant preacher. He died on 1 April 1702, and was buried at Chapel-en-le-Frith.
His Life and Funeral Sermon was published by John Ashe (1704), the main source of information concerning him.
He left manuscripts (fifty volumes) but little survived. His published books are all short. Their (abbreviated) titles are:
- 'Waters for a Thirsty Soul, in several sermons on Rev. xxi. 6.' London, 1653
- 'Of Christ's Purchase', to which is prefixed his 'Confession of Faith'
- 'Rules for our Behaviour every Day and for sanctifying the Sabbath, with Hints for Communicants'
- 'The Ready Way to prevent Sin' on Prov. xxx. 22, with 'A Bridle for the Tongue,' on St. Matt. X. 36
- The 'Miner's Monitor'
- The 'Sinner in Sorrow and the Humble Sinner's Modest Request'
- 'Brief Directions for the Improvement of Infant Baptism'
- The 'Riches of Grace' three parts
- 'Trading Spiritualized' three parts
- 'De Spiritualibus Pecci: Notes concerning the Work of God, and some that have been walkers together with God in the High Peak of Derbyshire' a biographical work (London, 1702)
- 'Principiis Obsta' 1671
- 'Sheet for Sufferers'
- 'Matters for Mourning', posthumous
- 'Essays on Union to Christ', posthumous
- This article incorporates text from a publication now in the public domain: "Bagshaw, William". Dictionary of National Biography. London: Smith, Elder & Co. 1885–1900.