Matthew Thornton was a Presbyterian and a devout Christian.
He was identified as a Presbyterian by the Presbyterian Historical Society and the Presbyterian Church, USA. (Source: Ian Dorion, "Table of the Religious Affiliations of American Founders", 1997).
From: B. J. Lossing, Signers of the Declaration of Independence, George F. Cooledge & Brother: New York (1848) [reprinted in Lives of the Signers of the Declaration of Independence, WallBuilder Press: Aledo, Texas (1995)], page 21:
Dr. Thornton was greatly beloved by all who knew him, and to the close of his long life he was a consistent and zealous Christian. He always enjoyed remarkably good health, and by the practice of those hygeian virtues, temperance and cheerfulness, he attained a patriarchal age.From: B. J. Lossing, Signers of the Declaration of Independence, George F. Cooledge & Brother: New York (1848) [reprinted in Lives of the Signers of the Declaration of Independence, WallBuilder Press: Aledo, Texas (1995)], pages 20-21:
When the provincial government of New Hampshire was organized, on the abdication of Governor Wentworth, Dr. Thornton was elected president. When the provincial Congress was organized he was chosen Speaker of the House [January 1776]. In September of the same year, he was appointed a delegate to the Continental Congress for one year, and was permitted to sign his name to the Declaration of Independence, when he took his seat in November. In January 1776, (prior to his election to the Continental Congress) he was appointed a judge of the Superior Court of his State, having previously been elected a member of the Court of Common Pleas. In December of that year, he was again elected to the general Congress for on year from the twenty-third of January, 1777. At the expiration of the term he withdrew from Congress, and only engaged in public affairs as far as his office as judge required his services. He resigned his judgeship in 1782.From: Robert G. Ferris (editor), Signers of the Declaration: Historic Places Commemorating the Signing of the Declaration of Independence, published by the United States Department of the Interior, National Park Service: Washington, D.C. (revised edition 1975), pages 139-140:
Thornton was born in Ireland about 1714. Approximately 4 years later, his Scotch-Irish parents emigrated with their family to America... His grave is in Thornton's Ferry Cemetery, near the site of his Merrimack home.