Mosonmagyaróvár is a town in Gyor-Moson-Sopron county in northwestern Hungary. It lies close to both the Austrian and Slovakian borders and has a population of 32,752 (as of 2015).

Mosonmagyaróvár used to be two separate towns, Magyaróvár and Moson. The town of Moson was the original capital of Moson county in the Kingdom of Hungary, but the county seat was moved to Magyaróvár during the Middle Ages. The two towns were combined in 1939, and by now almost all signs of dualism have disappeared, as the space between the two towns has become physically and culturally developed. Due to the name's length, Mosonmagyaróvár is also referred to as Óvár amongst locals and Moson by foreigners. The Hansági Museum can be found in Mosonmagyaróvár.

The name Moson comes from the Slavic, in the wider meaning moss-covered mud, marsh.

Magyaróvár literally means "ancient Hungarian castle" in Hungarian, though the Magyar prefix was only added to the name after confusion with a similarly named town in Austria called Németóvár, which literally means "ancient German castle". The "ancient castle" being referred to is the ruins of the Roman fortress, Ad Flexum. 1271 Altenburch.

The names were simply combined when the two towns were administratively unified (as with Budapest), rather than hyphenated ("Moson-Magyaróvár").