Walter Jeremiah Maddock (September 13, 1880 – January 25, 1951) was an American politician in North Dakota, US. He served in the North Dakota House of Representatives from 1915 to 1923, and became the 14th Lieutenant Governor of North Dakota in 1925. Maddock became the 15th Governor of North Dakota in 1928 when Arthur G. Sorlie died in office. He was the first governor born in what would eventually become North Dakota.

He was born in Grand Forks, Dakota Territory. He was educated at Northwestern Business College in Grand Forks, North Dakota.^[1] He was married on October 30, 1906, to Margarite Tierney. They had five children: Wallace, Jerome, Dore R. V., Bernard, and Margarite.^[2]

Maddock's first involvement with politics was as one of the founders of the Nonpartisan League.^[3] He was a member of the North Dakota House of Representatives from 1915 through 1923.^[4] He became the Lieutenant Governor in 1925, and upon the death of Governor Sorlie, he assumed the governorship in 1928. He served the remainder of Sorlie's term and sought re-election, but he failed to win the race against George F. Shafer. In the 1928 election, he took the unusual step of switching parties from Republican to Democratic.

After being defeated in the election, Maddock returned to farming and was active in organizing farmers' cooperatives. He was a very strong supporter of the Nonpartisan League, and he also supported two state-owned industries, the Bank of North Dakota and the State Mill and Elevator.^[5] In 1933, he became the senior administrative officer of the regional Agricultural Adjustment Administration. From 1937 until his retirement in 1950, he served as the head of North Dakota's Farm Security Administration office.

Maddock died on January 25, 1951, and is buried in Saint Mary's Cemetery, Bismarck, Burleigh County, North Dakota, US.