Thomas Ellwood (October 1639 – 1 March 1714) was an English religious writer. He is remembered for his relationship with poet John Milton, and some of his writing has proved durable as well.
Ellwood was born in the village of Crowell, Oxfordshire, the son of a rural squire, Walter Ellwood, by his wife, Elizabeth Potman. From 1642 to 1646 the family lived in London. He was educated at Lord Williams's School in Thame.
Ellwood became a Quaker after visiting Isaac Penington and his family at Chalfont St. Peter in Buckinghamshire. Penington's wife, Mary, widow of Sir William Springett, had known the Ellwoods while they lived in London. On a second visit in December 1659, when Thomas attended a Quaker meeting at a neighbouring farmhouse and made the acquaintance of Edward Burrough and James Nayler. Burrough's preaching impressed Ellwood, and after attending a second meeting at High Wycombe he joined the new sect and adopted their modes of dress and speech. His father resented his son's conversion, thrashed him for wearing his hat in his presence, and kept him confined in the house through the winter of 1660. Neither blows nor persuasion could induce Ellwood to renounce his new sentiments, to take off his hat before his parents, or to address them with other pronouns than “thou” and “thee.” At Easter, the Peningtons managed to move him to Chalfont St. Peters, where he stayed till Whitsuntide. He attended meetings with great assiduity.
In 1660 Ellwood was divinely inspired, according to his own account, to write and print an attack on the established clergy entitled An Alarm to the Priests. He later visited London and met George Fox the younger. About November 1660 Ellwood invited a Quaker from Oxford named Thomas Loe to attend a meeting at Crowell. Loe was at the time in prison in Oxford Castle, and Ellwood's letter fell into the hands of Lord Falkland, lord-lieutenant of the county. A party of horse was sent to arrest him: he was taken before two justices of the peace at Weston, refused to take the oaths of allegiance and supremacy, and was imprisoned for some months at Oxford in the house of the city marshal, a linendraper in High Street named Galloway. His father secured his release and tried to keep him from Quaker meetings.