The biggest tank battle in history?

The Battle of the Kursk, in the summer (July-August) of 1943 on the Russian front of WW2 is by far the largest armored combat ever, with approximately 8,000 tanks.

The biggest single-day armored battle was the Battle of Prokhorovka (12 July 1943), a part of the Battle of Kursk; the main combatants were the German II SS Panzer Corps and the Russian 5th Guards Tank Army. Roughly 1,500 tanks were involved, with about 800 destroyed or damaged in that single day.