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

In the Middle and Modern Ages, the settlement was a little market town in the western part of Komárom county.

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.