The Coonan Cross Oath, also known as the Great Oath of Bent Cross, the Leaning Cross Oath or the Oath of the Slanting Cross, taken on 3 January 1653 in Mattancherry, was a public avowal by members of the Saint Thomas Christians of the Malabar region in India, that they would not submit to the Jesuits and Latin Catholic hierarchy, nor accept Portuguese dominance in ecclesiastical and secular life.

The Malankara Church, also known as Puthenkur, is the historic unified body of West Syriac Saint Thomas Christian denominations which claim ultimate origins from the missions of Thomas the Apostle. This community, under the leadership of Thoma I, opposed the Padroado Jesuits as well as the Propaganda Carmelites of the Latin Church, following the historical Coonan Cross Oath of 1653. The Malankara Church's divisions and branchings have resulted in present-day Churches that include the Jacobite Syrian Christian Church, the Malankara Orthodox Syrian Church, the Malankara Mar Thoma Syrian Church, the Malabar Independent Syrian Church, the Syro-Malankara Catholic Church, the Saint Thomas Anglicans of the Church of South India and the St. Thomas Evangelical Church of India.