The largest filled dam in the world by reservoir volume is the Kariba Dam, located on the Zambezi River between Zambia and Zimbabwe.
Its reservoir, Lake Kariba, has a storage capacity of 185 billion cubic meters (km³) of water when full.
However, if you mean the largest dam by structural volume (the amount of material used to build it), that title goes to the Tarbela Dam in Pakistan, with a structural volume of about 153 million cubic meters.
If you are asking about the largest dam by height, that would be the Jinping-I Dam in China at 305 meters tall.
So, depending on the specific metric:
Let me know if you meant a different measure of “largest”!