Shirley Waldemar Baker (1836[1] – 16 November 1903) was a Methodist missionary in Tonga. He was the founder of the Free Church of Tonga and enjoyed significant influence during the reign of George Tupou I, who made him prime minister.

In 1860, Baker was ordained as a Wesleyan minister and went to Tonga as a missionary. He became head of the mission and was involved in the councils of King George Tupou I, who made him his prime minister in 1880. A disagreement arose with the Wesleyan authorities at Sydney in 1879, and Baker founded an independent body under the title of the "Free Church of Tonga". Some of the natives, however, were loyal to their original church and much strong feeling was aroused, which resulted with an attempt to shoot Baker in 1887. He escaped unhurt, but his son and daughter were both wounded. Six Tongans were executed for this crime,[1] and many were deported to other islands. In 1888, the Rev. George Brown visited Tonga to inquire into the position and to endeavour to heal the breach between the two churches. He did not succeed, and his reports show that Baker was using his power to the disadvantage of those who were not adherents of the Free Church. In 1890, Sir John Bates Thurston visited Tonga and deported Baker at short notice to Auckland for being 'prejudicial to the peace and good order of the Western Pacific'.