William Moulton Ingraham (1870 – October 13, 1951) was an American politician from Portland, Maine. A Democrat, Ingraham was elected Mayor of Portland in December 1915. He served one term in that position and was replaced the following year by Republican Wilford G. Chapman. He was then appointed United States Assistant Secretary of War from 1916 to 1917 in the Woodrow Wilson administration.
He was born in 1870 to Ella Moulton and Darius H. Ingraham. His father, Darius, served as Mayor from 1891 to 1893. He was a graduate of Bowdoin College in the class of 1895. He died on October 13, 1951.