Sulphur is a city in and county seat of Murray County, Oklahoma, United States. The population was 4,929 at the 2010 census, a 3.4 percent gain over the figure of 4,794 in 2000. The area around Sulphur has been noted for its mineral springs, since well before the city was founded late in the 19th century. The city received its name from the presence of sulfur in the water.