Fr. Augustine Baker OSB (9 December 1575 – 9 August 1641), also sometimes known as "Fr. Austin Baker", was a well-known Benedictine mystic and an ascetic writer. He was one of the earliest members of the English Benedictine Congregation which was newly restored to England after the Reformation.
Augustine Baker was born David Baker at Abergavenny, Monmouthshire on 9 December 1575. His father was William Baker, steward to Baron Abergavenny, and his mother was a daughter of Lewis ap John (alias Wallis), vicar of Abergavenny. His parents were "church papists" , meaning that although outwardly they conformed to Anglican worship, they remained Catholic by conviction 
He was educated at Christ's Hospital and at Broadgate's Hall, now Pembroke College, Oxford, afterwards becoming a member of Clifford's Inn, and later of the Middle Temple. In 1598 he was made Recorder of Abergavenny.
At Oxford he lost his faith in the existence of God, but after some years, being in extreme peril of death, he escaped by what appeared to him a miracle. Following this, he was led to the threshold of the Catholic Church, and was received into its fold.
In 1605 he joined the Benedictine Order at the Abbey of Santa Giustina, taking the religious name "Augustine", but ill health obliged him to postpone his religious profession, and he returned home to find his father on the point of death. Having reconciled him to the Catholic Church and assisted him in his last moments, Baker hastened to settle his own worldly affairs and to return to the cloister. He was professed by the Italian Fathers in England as a member of the Cassinese Congregation, but subsequently aggregated to the English Congregation.
At the desire of his superiors he now devoted his time and the ample means which he had inherited, to investigating and refuting the recently started error that the ancient Benedictine congregation in England was dependent on that of Cluny, founded in 910. He used the Cottonian Library, which contained many works from Benedictine monasteries in England, placed at his disposal. In collaboration with Father Jones and Father Clement Reyner he wrote up his research in Apostolatus Benedictorum in Anglia. At Sir Robert Cotton's, Baker came in contact with the antiquary William Camden and with other learned men of his day.
In 1624 he was sent to the newly established convent of Benedictine nuns at Cambrai (today succeeded by the community at Stanbrook Abbey) in Flanders, not as chaplain, but to aid in forming the spiritual character of the religious. Here he remained for about nine years, during which time he wrote many of his mystical treatises, an abstract of which is contained in the valuable work Sancta Sophia (1657) compiled by Father Serenus Cressy. In 1633 he removed to Douai, where he wrote his long treatise on the English mission, but he was nearly worn out with his austerities before the order came for him to proceed to the battlefield. During his short stay in London, Baker was frequently forced to change where he stayed in order to avoid those tracking him.
Of more than thirty treatises chiefly on spiritual matters written by Baker, many are to be found in manuscript at Downside Abbey, Ampleforth Abbey, Stanbrook Abbey, and other Benedictine monasteries in England.
Abbot Justin McCann, Master of St Benet's Hall, Oxford (1921–47) and titular Abbot of Westminster from 1947, remains the principal modern editor and interpreter of Baker, with the claim that he is the only man since Fr Cressy to have read all two million words of his writings, always diffuse and unstructured.
- Sancta Sophia ("Holy Wisdom", 1657) compiled and edited by Serenus Cressy.
- Herbermann, Charles, ed. (1913). "David Augustine Baker". Catholic Encyclopedia. New York: Robert Appleton Company.