Apollinaris William Baumgartner, OFMCap, D.D., (24 July 1899 – 18 December 1970) was a prelate of the Catholic Church, serving as Bishop of Agaña, Guam, from 1945 to 1970.

[3] He arrived in Guam on 23 October 1945, shortly after the end of the World War II, flying in on the personal plane of Admiral Chester W. Nimitz,[4] who was leading the post-war military administration on the island.

[5] Almost immediately after arriving on Guam, Baumgartner set to work reestablishing Catholic schools on the island, all of which had been destroyed in the war.

[1] He quickly arranged for religious sisters to set up houses on the island to staff his schools, while also hiring Chamorro lay teachers.

[4] Besides founding schools, he was also active in acquiring scholarships for Chamorro children to Catholic seminaries, colleges, and universities on the mainland United States.

[7] On 14 October 1965, the Vicariate Apostolic of Guam was raised and renamed the Diocese of Agaña, and Apollinaris Baumgartner was appointed its first bishop.