Juhanon Mar Thoma XVIII (7 August 1894 – 27 September 1976) was the Metropolitan of the Malankara Mar Thoma Syrian Church from 1949–1976, who gave leadership to the church and at the same time actively participated in social and political arenas.

His father was C. P. Mathew Munsiff (judge) Cherukara Paravelithundiyil, Ayroor, in Kerala.

He was attracted to Indian Nationalism, and started to wear Khadi, following the principles of Mahatma Gandhi.

He was able to meet a number of foreign missionaries that made him decide to select gospel work as his ambition.

After completing his education at Madras, he joined the United Theological College, Bangalore, and obtained BD Degree in 1922.

For six years after leaving Bangalore he was teaching at Mar Thoma Seminary High school, Kottayam.

In 1928 he left for higher studies at Union Theological Seminary in the city of New York.

Third World Scout Jamboree was held Birkenhead, England in 1929 from 31 July to 6 August.

His tireless work affected his health and he had to retreat to a sanatorium for rest and treatment.

For this purpose, a special chair was made and Mar Thoma I the first bishop of Malankara church was enthroned.

To enhance the work of the church it was decided to consecrate two more bishops and the lot fell to John and C. T. Mathew.

During this period, members of the Mar Thoma church spread to Malaya, Singapore, and the Gulf region in addition to various parts of India.

Even before the consecration of the three bishops, Mr. K. N. Daniel, Kurumthottical, a renowned church historian and seminary professor criticised Juhanon Mar Thoma and accused him of going against the reformation ideals.

P. T. Joseph and V. T. Koshy were consecrated bishops by Juhanon Mar Thoma in February 1975.

At that time on 25 August 1976, Juhanon Mar Thoma sent a letter to the Prime Minister arguing for the restoration of democracy.

In 1974, Mar Thoma Theological Seminary was upgraded to a BD Undergraduate college affiliated to the Serampore University.

In 1967, before moving to the new residence built for the Metropolitan (known as Poolatheen), he made it a point to present a house to a poor homeless TB patient who was a non-Christian.