Richard William Guenther (November 30, 1845 – April 5, 1913) was a German American immigrant, pharmacist, and Republican politician. He served eight years in the United States House of Representatives, representing central Wisconsin, and was the 8th State Treasurer of Wisconsin.

Born in Potsdam, in the Province of Brandenburg, in what was then the Kingdom of Prussia, Guenther received a college education and graduated from the Royal Pharmacy in Potsdam. He immigrated to the United States in 1866, settling in New York City. He moved to Oshkosh, Wisconsin, in 1867 and engaged in the pharmaceutical business.

Guenther was Wisconsin State Treasurer from 1878 to 1882 and was elected as a Republican to the United States House of Representatives in 1880. He first represented Wisconsin's 6th congressional district for three terms (March 4, 1881 - March 3, 1887). After redistricting, he represented Wisconsin's 2nd congressional district for one term (March 4, 1887 - March 3, 1889). Overall, Guenther represented Wisconsin from the 47th through the 50th Congresses.

Guenther was appointed consul general in three different locations: in Mexico City, Mexico by President Benjamin Harrison in 1890, serving until 1893; in Frankfurt, Germany by President William McKinley in 1898, serving until 1910; and in Cape Town, South Africa by President William Howard Taft in 1910, serving until his death in Oshkosh, Wisconsin on April 5, 1913. He was interred in Riverside Cemetery in Oshkosh.

The Richard Guenther House in Oshkosh is listed on the U.S. National Register of Historic Places.^[1]