Sibthorpe, Sir Christopher (d. 1632/3), judge and religious writer, was third son of John Sibthorpe of Much Bardfield, Essex, England; no details of his mother are known. He matriculated at Cambridge before entering Middle Temple (1584) and was called to the bar (1594). He was appointed third justice of king's bench in Ireland in 1607 and was in Ireland by that summer. In December 1607 he was sent into Ulster to indict the fugitive earls of Tyrone (qv) and Tyrconnell (qv). Indeed, between summer 1607 and summer 1615 he would ride the Ulster circuit seventeen times. Due to his great familiarity with the province, he was sent twice to Ulster in 1612 to resolve disputes between planters and natives involving the plantation of Ulster. In 1613–15 he was an active member of the Irish parliament as MP for Limavady. He was knighted in 1618 and subsequently became treasurer of King's Inns.
As well as being well versed in law, he was a serious theological scholar. His views were strongly puritan and often at odds with the established church; in 1588, he had been expelled from Middle Temple for nonconformity. Around 1612 he wrote a work which, though it has not survived, attracted the interest of James Ussher (qv), renowned scholar and future archbishop of Armagh. Having been encouraged and assisted by Ussher, he published A friendly advertisement to the pretended catholicks of Ireland. Despite its title, it was a rather crude anti-catholic polemic, which stressed that the pope was the Antichrist described in the Book of Revelations. This publication also involved the first use of Hebrew type in Ireland.
In response to catholic rebuttals, circulated in Ireland in manuscript form, he published two further theological polemics: A reply to an answer (1625) and A surreplication to the rejoinder of a popish adversarie (1627). His Friendly advertisement and Surreplication attracted enough interest to require second editions. In his later years he drafted revised editions of his last two works and a new work directed against the religious writings of the Irish Jesuit William Malone (qv), but these were never published, presumably due to his death. He died between May 1632 and March 1633. He married, but nothing is known of his wife and he does not appear to have had any children.