Mason is a city in the Warren County of the state of Ohio in the United States. It is one of the fastest growing cities in the US and up until 1997, it held the top spot. As of the 2000 census, Mason had an estimated population of 22,016.

.Revolutionary war veteran William Mason purchased 640 acres of land, now known as downtown Mason, in 1803 for US$ 1,700. He platted several lots in the area, which was expanded further after his death, and called it Plamyra. A 1835 petition called for the official renaming of the city to Palmyra. Unfortunately, another Ohio city had claim to that name, the residents instead voted to have the city named 'Mason' after its founder.

The city is served by two interstates the I-71 and the I-75. CNN Money has ranked mason as one of the top 100 places to live in the United States. Tourist spots found in Mason include the Kings Island amusement park, Great Wolf Lodge Hotel and Indoor Watepark and The Beach Waterpark. The city is also the home of Procter and Gamble's Mason Business Center as well as the Lindner Family Tennis Center. The latter is the home of the Cincinnati Master's Tennis tournament.

Mason City Schools are one of the top school systems in Ohio. The city school district has received several Ohio Blue Ribbons. Several of its graduates have also gone on to attend Ivy League Schools and even more graduated as national merit scholars or commended merit scholars.

Notable residents resident from Mason include Dan Patrick, who was a sportscaster and former ESPN employee. Actor George Clooney also made his home in Mason from 1968 to 1975.