Veľký Meder (1948–1990 Čalovo, Hungarian: Nagymegyer, Yiddish: Magendorf) is a town in the Dunajská Streda District, Trnava Region in southwestern Slovakia.

During the period of 1914-18 (World war I), near the town's railway station, was the location of the Austro-Hungarian death camp Kriegsgefangenenlager Nagymegyer.

The Serbian cemetery in Veľký Meder has mass graves and monument to 5,153 Serb and Montenegrin war prisoners who died in the Kriegsgefangenenlager Nagymegyer, Austro-Hungarian POW camp.

After the Austro-Hungarian army disintegrated in November 1918, Czechoslovak troops occupied the area, later acknowledged internationally by the Treaty of Trianon.

According to the 2001 census, the most dominant group in the town are the Hungarians (84.6%), next are the Slovaks (13.5%), and there are small minorities of Czechs and Romani (both 0.7%).