| William Q. Dallmeyer | |
| Office: | Treasurer of Missouri |
| Term Start: | 1869 |
| Term End: | 1871 |
| Predecessor: | William Bishop |
| Successor: | Samuel Hays |
| Birth Date: | 23 October 1829 |
| Birth Place: | Hanover, Germany |
William Quintillian Dallmeyer (October 23, 1829 – March 15, 1908) was an American politician in the state of Missouri.
William Quintillian Dallmeyer was born in Hanover, Germany.[1] He emigrated to the United States in 1845, living in New York City and New Orleans, Louisiana, before settling in St. Louis, Missouri, where he worked in the dry goods business. In 1856, he moved to Gasconade County, Missouri, where he divided his time between his farm, general store, and serving as the local postmaster and Justice of the peace. In 1864, he was elected to the Missouri House of Representatives, serving until 1869, when he was elected State Treasurer. Following his two-year term as State Treasurer, he served as cashier at the First National Bank in Jefferson City, Missouri, from 1874 to 1882, and subsequently as cashier and president of the Exchange Bank.