thumb|right|Martin Boos
Martin Boos (25 December 176229 August 1825) was a German Roman Catholic theologian.
Life
He was born at Huttenried in Bavaria. Orphaned at the age of four, he was reared by an uncle at Augsburg, who finally sent him to the University of Dillingen, where he studied under Sailer, Zimmer, and Weber. There he laid the foundation of the modest piety by which his whole life was distinguished. He had followed the extreme practices of asceticism as a penance for sin, all to no avail, as he believed, and then developed a doctrine of salvation by faith which came very near to pure Lutheranism. This he preached with great effect.
After serving as priest in several Bavarian towns, he was driven from Bavaria by the opposition of the ecclesiastical authorities and other priests. He made his way in 1799 to Linz in Austria, where he was welcomed by Bishop Gall, and set to work first at Leonding and then at Waldneukirchen, becoming in 1806 pastor at Gallneukirchen. His pietistic movement won considerable way among the Catholic laity, and even attracted some fifty or sixty priests.