Alfred Berthier Olsen (June 26, 1869 – August 8, 1960) was an American physician, Seventh-day Adventist and vegetarian.

[1] His father was Seventh-day Adventist minister Ole Andres Olsen.

[3] Olsen was active in the early development of Seventh-day Adventist medical work and conducted lecture tours in Scotland and Wales.

[2] Olsen's book School of Health (1906) promoted exercise, hygienic practices and a vegetarian diet.

[5] Olsen was a Fellow of the American College of Physicians and the Royal Society of Medicine.