| John M. Zwach Sr. | |
| Birth Date: | February 8, 1907 |
| Birth Place: | Gales Township, Redwood County, Minnesota, U.S. |
| Death Place: | Lucan, Minnesota, U.S. |
| State: | Minnesota |
| District: | 6th |
| Term Start: | January 3, 1967 |
| Term End: | January 3, 1975 |
| Predecessor: | Alec G. Olson |
| Successor: | Richard Nolan |
| Office2: | Minnesota Senate Majority Leader |
| Term Start2: | January 6, 1959 |
| Term End2: | January 2, 1967 |
| Predecessor2: | Archie H. Miller |
| Successor2: | Stanley W. Holmquist |
| Office3: | Member of the Minnesota State Senate |
| Term Start3: | January 7, 1947 |
| Term End3: | January 2, 1967 |
| Successor3: | Carl Jensen |
| Office4: | Member of the Minnesota House of Representatives |
| Term Start4: | January 8, 1935 |
| Term End4: | January 6, 1947 |
| Party: | Republican |
| Occupation: | School Principal Teacher |
| Alma Mater: | University of Minnesota Minnesota State University, Mankato |
| Spouse: | Agnes |
| Children: | 5, including Barbara |
John Matthew Zwach Sr. (February 8, 1907 - November 11, 1990) was an American farmer, rural school teacher, and politician. Zwach was most notably a U.S. Representative from Minnesota, serving four terms from 1967 to 1975. He also served for several terms in the Minnesota legislature.
Zwach was born in Gales Township, Redwood County, Minnesota, the son of Austrian immigrants. He attended the public schools and graduated from Milroy High School in 1926. He then received a teaching certificate from Mankato State College (now Minnesota State University, Mankato) in 1927 and graduated from the University of Minnesota in 1933. He worked as a school teacher and superintendent for fourteen years and was also an active farmer.
Zwach served in the Minnesota House of Representatives from 1934 to 1946. He was a member of the Minnesota Senate from 1946 to 1966 and was the majority leader from 1959 to 1966, leading the Conservative Caucus in the nonpartisan body. He was also a member of the Interim Agriculture Commission, 1955 - 1957.
He was elected as a Republican to the 90th, 91st, 92nd and 93rd congresses, (January 3, 1967 - January 3, 1975). He was not a candidate for reelection in 1974.
He was a resident of Lucan, Minnesota until his death on November 11, 1990. He was buried at St. Michael's Cemetery.
His daughter, Barb Sykora, served in the Minnesota House of Representatives from 1995 to 2007.