Thomas Bailey or Bayly (died c. 1657) was a seventeenth-century English religious controversialist, a Royalist Church of England clergyman who converted to Catholicism.
He served as a commissioned officer in defence of Raglan Castle in 1646, and was briefly imprisoned in Newgate gaol for writing against the Commonwealth after Charles I was executed in 1649.
In Certamen Religiosum he reported on religious discussions from 1646 between Charles and Henry Somerset, 1st Marquess of Worcester, at Raglan Castle.
[2] The work proved controversial, and was attacked by Hamon L'Estrange,[3] Christopher Cartwright, and Peter Heylyn.
A Life of John Fisher was issued under Bailey's name in 1655, though it was in fact a re-publication of a much earlier text which Richard Hall (died 1604) had translated into Latin.