Milton Dwight Purdy (November 3, 1866 – February 11, 1937) was a United States federal judge.
Born in Mogadore, Ohio, Purdy received an A.B. from the University of Minnesota in 1891 and an LL.B. from the University of Minnesota in 1892. He was an assistant city attorney of Minneapolis, Minnesota from 1893 to 1897 and an assistant county attorney of Hennepin County, Minnesota from 1897 to 1898 before becoming an assistant U.S. Attorney for Minnesota from 1898 to 1901. He was the U.S. Attorney for the District of Minnesota from 1901 to 1902. He was an assistant U.S. Attorney General in Washington, D.C. from 1903 to 1905, and an assistant to the U.S. Attorney General from 1905 to 1908.
On July 6, 1908, Purdy received a recess appointment from President Theodore Roosevelt to a seat on the United States District Court for the District of Minnesota vacated by William Lochren. Formally nominated on December 8, 1908, Purdy's service was terminated on March 3, 1909, after his nomination was not confirmed by the Senate. Purdy then received a recess appointment to the same seat from President William Howard Taft on March 6, 1909, but Purdy resigned on May 1, 1909, before the matter was considered by the Senate.
From 1902 to 1904, Purdy was a special assistant to the U.S. Attorney General, and from 1924 to 1934 he served as a judge on the United States Court for China in Shanghai, China.
Purdy died in Honolulu, Hawaii.