Spencer Milton Marsh (July 26, 1864 – October 11, 1932) was an American jurist and legislator.

Marsh served as a Republican member of the Wisconsin Senate, representing the 25th District.

He attended the state Normal School at River Falls in 1882 and 1883.

[1] He served as the district attorney for Clark County for two terms, having been elected to the Republican ticket in 1898 and 1900.

He served as District Attorney for San Diego County, California and in 1917 served as San Diego County Superior Court judge.