Primghar is a city in and the county seat of O'Brien County, Iowa, United States, United States. The population was 891 at the 2000 census.
In a brief history of O'Brien County, Arthur M. Schierholz states: "the courthouse location in (the village of) O'Brien in the extreme southeast corner of the county became a growing issue. To resolve the matter, an election was held on November 11, 1872, to determine the location of the courthouse." A total of 360 votes were cast, with 307 voting to move the courthouse to the exact geographical center of the county. Another historian wrote, "Probably the only case in Iowa, perhaps anywhere, where a bare spot of raw prairie was actually voted to be the county seat." This eventually became the town of Primghar. The present O'Brien County Courthouse was completed in 1917. The name Primghar was received from the first letter of eight people who had a major part in platting the town.
Primghar is located at 43°5′16″N 95°37′40″W / 43.08778°N 95.62778°W / 43.08778; -95.62778 (43.087722, -95.627892).