Mu De (1865-1955), an American originally named John R. Mott, was a missionary activist of Christianity in the 20th century.

In 1885, he chose missionary work as his lifelong career. He became the chairman of the executive committee of the Student Volunteer Movement for Foreign Missions in 1888, and began to tour around the world preaching. With Karl Fries of Sweden, he organized the World's Student Christian Federation in 1895. In 1921, he founded the World Missionary Conference. Due to his outstanding contributions in the two world wars, he was honored Nobel Peace Prize in 1946.

He went to missionize and preach in China several times. In 1922, he collaborated with others to establish the Church of Christ in China, which greatly promoted Christianity in China in the first half of the 20th century.